Unit 8 Enzymes Flashcards

reduces the activation energy of a reaction. Acts as a catalyst. (The Lock)

a protein that decreases the activation energy of a reaction

:specific form of an enzyme, different isoenzymes can perform the same exact function, they just look a little different, or they may go about it in a slightly different manner. (The color of the lock, or how the lock looks)

: non-protein molecule necessary for enzyme activity (Tumblers inside the lock)

- inorganic and organic compounds that are required for full enzyme function

The complete form of a functional enzyme unit complete with cofactors (Lock with the tumblers)

The enzyme portion of a Holoenzyme, may or may not be active (The casing around the lock. looks like a lock, but does it lock?

an inactive enzyme without its cofactor

an organic cofactor, AKA prosthetic group. (The metal key guard that you rotate to the side to insert the key)

- organic cofactors that commonly have a structure related to vitamins

- Oxidize or Reduce substrates

Transfer side groups (e.g. NH 3 ) between substrates

Add water to break apart a substrate

- Breaks apart chemical bonds of a substrate

- Interconvert between forms of a substrate (think transforming)

- Join together two organic substrates into one

Oxidoreductase

S + E → ES → E + P
S = Substrate E = Enzyme P = Product

To reduce the activation energy of a reaction. This will subsequently increase the likelihood that this reaction will occur, and the amount of product that is being formed.

All of the enzyme binding sites are full and the enzyme is working at maximum capacity. A further increase in substrate concentration will NOT be able to increase the reaction speed.

Competitive inhibition

International Units

Simple reactions like hydroxylation, oxidation, or reduction to make the drug more water soluble.

The correct answer is D) This is caused because it is
metabolized by the CYP450 enzyme system. If Ketoconazole inhibits this enzyme, then less phenytoin will be metabolized and more will remain in circulation, causing more drug to be in the blood than calculated. The Ketoconazole does NOT cause the phenytoin to
become more active (A), nor does it render the phenytoin ineffective (B), or create a subtherapeutic level of the drug (C).

The correct answer is D) . When we have
an excess of substrate, and we know how much enzyme we put in the reaction, we know exactly how fast the reaction can go at different concentrations of enzyme. With this knowledge, we then can compare the unknown sample to a reference reaction speed to infer the concentration. All of the available binding sites on the enzymes are occupied and the enzyme is working as fast as it can. The rate is dependent upon how much
enzyme there is in the reaction.

The correct answer is C) . The total Vmax is decreased, which basically means that the inhibitor renders the bound enzyme obsolete in catalyzing the reaction. Noncompetitive inhibitors bind to sites on the enzyme other than the active site for the substrate, therefore, they do not compete for the binding site. When these
Noncompetitive inhibitors bind, they usually cause a conformational change in the enzyme, which will block the substrate from binding and the reaction from being
catalyzed. This effect may be a permanent disfiguration of the enzyme or it may just be a temporary one. This deformed shape may improve when the noncompetitive inhibitor
dissociates.

Yes, CK is positively correlated with muscle mass.

HHHH

heart, RBCs, kidney. Are elevated in heart attacks

HHHM

lungs, RBCs

HHMM

spleen, lungs, and many tissues

HMMM

liver and skeleton

MMMM

liver and skeleton

Primary tissues: Heart, RBCs

High-Yield defects which cause elevation: Myocardial infarction, hemolytic anemia

Primary tissues: Heart, RBCs

High-Yield defects which cause elevation: Myocardial infarction

Primary tissues: Lung, Lymphocytes, Pancreas

High-Yield defects which cause elevation:

Acute pancreatitis, pneumonia

Primary tissues: Liver

High-Yield defects which cause elevation: Hepatic injury

Primary tissues: Liver, Skeletal Muscle

High-Yield defects which cause elevation:

Hepatic injury, skeletal muscle injury

His LD isoenzyme panel would show the 1,2 Flip. LD-1 is higher than LD-2. This is a stereotypical pattern for patients with myocardial infarctions.

Kidney, Liver, Muscle, and RBCs

Hemolysis in the tube

Liver

G6PD deficiency

The correct answer is B) Other cardiac biomarkers that would help out in this scenario would be any of the troponins, Tn-I, Tn-C, or Tn-T. Remember that these biomarkers stay elevated for a long time after the other acute biomarkers have dropped off in concentration. Tn elevates quickly and remains elevated for a long time, that makes this marker the most specific marker when we are trying to determine a distant heart attack. LD can come from many sources, so it is not as specific to the heart.
An elevation in LD should probably be followed up with a more specific marker, like Tn.

The correct answer is B) There’s a lot going on in this question,
so let’s break it down a little bit at a time. What I wanted you to pick up on, is that she only has one suggestion that she’s here for alcoholic hepatitis, but the AST/ALT ratio is only 1.4, so it means that she might have been drinking tonight, but she maybe does it
once a year or so, not often enough to cause lasting liver damage, because her DeRitis ratio is less than 2. Her clinical history is quite suspicious for an autoimmune disease. First, she’s a female, and females get them a lot more often than males do. Next, she
has a family history of autoimmune diseases, which places her at an increased risk. Next is the prognostic sign of the productive capacity of the liver. We create most of our clotting factors in our liver, and if our liver is damaged, then we can’t produce as many of them. Likewise, the more damaged our livers are, then the more impaired our clotting factor production will be. This will lead to an increase in clotting times and probably an INR >2.
A) Long-term alcoholic hepatitis would be suggested if her AST/ALT ratio were above 2.
C) Hepatitis D infections are fairly rare, and require a coinfection with Hepatitis B.
D) Bacterial hepatitis may be possible, but she has no systemic signs of infection, just liver failure

The correct answer is C) These isoenzymes are fairly specific
to the liver. Not enough time has elapsed for CK-MB, Tn-I, LD, or AST to be elevated from the cardiac source. So they will have to keep him in the hospital for about 8 hours to rule out the myocardial infarction. Bone disease is one that can commonly cause elevation in LD-5, but it does not result in an increased LD-4. this allows for fairly easy
differentiation between the two. D) The 1,2 Flip is seen in a myocardial infarction, where LD-1 raises above the level of the LD-2 peak. B) LD-2 should be higher than all of the other isoenzyme peaks, but you can get into the specifics if you decide to do a Masters
or Doctoral program. A) Elevated LD-1 and LD-3 do not usually go together

Biliary tract, placenta, bone, kidney, liver

4 ng/mL. 5 - 1 = 4. Remember, prostatic ACP is susceptible to tartrate.

Prostatic secretions

If GGT were low, then that would rule-out a hepatobiliary source of the ALP

Destroy α-1, 4 glycosidic linkages

24, 2 from every triglyceride and 12 monoglycerides

The correct answer is B) Gallstone (Choledocholithiasis). AST and ALT will be elevated if there is liver damage so with this question stem, I am really only thinking about answers A and B. Remember that ALP and GGT are seen in extremely high concentrations in the bile ducts and that they will be increased in just about any bile duct
pathology, especially if you try to jam a stone through the pipe! The elevated ALP and GGT at these levels are NOT consistent with a diagnosis of A) hepatitis. The increased ALT value pretty much rules out the possibility of a C) Kidney stone or a D) Heart attack.

The correct answer is D) This is a long question stem with some great clinical pearls hidden within the question stem. Let’s go through them first and then we’ll go through the lab results. The groin pain radiating to his back sounds like a musculoskeletal thing or testicular torsion to me. The inability for complete evacuation of the bladder during urination is a hallmark for benign prostatic hypertrophy. We notice that this patient’s ALP is normal, so there is likely not a skeletal disease causing this issue. Pain relief with alcohol consumption is a typical finding. Alcohol not only dulls the nerves which dulls the pain, it also dulls the neurons in your brain to receive that pain.
All the results are normal except for the ACP, TRAP, and LPS. Who knows what happened with LPS. But he is NOT complaining of symptoms at this point that would lead me to think that there is a problem with absorbance of fat soluble vitamins or an energy deficiency. So this is likely NOT causing a problem and this patient might just fall out of the normal range since his value is barely elevated. The values that I want to look at are the elevated ACP and the low TRAP. Let’s calculate the prostatic portion of ACP:
10.1 - 1.5 = 8.6. The normal range for prostatic ACP is less than 4.08 IU/L. This is about double that value. That’s about double the value! No wonder he is having a problem peeing.

The correct answer is D) This enzymatic deficiency causes steatorrhea, which leads to what the experts call “foul-smelling stool” (as if poop didn’t normally smell bad). The jaundice is often caused by hepatocellular damage and inability to conjugate the bilirubin to excrete it. The weight loss comes from the inability to absorb fats. They’re all lost in the stool. We really only have one enzyme that would cause all of these fat-related issues, LPS! A) Amylase breaks down starches and carbohydrate chains. B) Glucagon is released
from the

the substance that is used up in the reaction

- the substance that is formed in the reaction

- a substance that prevents or inhibits a reaction from taking place

- the change of absorbance is measured on a spectrophotometer to assess the reaction rate . Have to do with speed

the change in absorbance is measured at the end of the reaction.

a unit of activity or potency for many substances defined individually in terms of the activity of a standard solution.

- the maximum velocity of an enzymatic reaction

the concentration of substrate which allows the enzyme to achieve half Vmax

the energy required to get the reaction started. Kind of like finding the energy required to get yourself off the couch on a lazy day

The reaction rate is dependent upon substrate and enzyme concentrations

The reaction rate is constant and dependent upon only the enzyme concentration

- coenzymes covalently bound to the enzyme

- is the apoenzyme and coenzyme in one catalytically active unit

- enzymes that have a metallic ion in them

- a 1:1 relationship between substrate and velocity

the reaction reaches an asymptote, all enzyme sites are occupied and the reaction velocity cannot be increased by addition of substrate

is the substrate concentration at which the reaction rate is half of Vmax

Same Vmax

different Km

Same Km

Different vmax

LD2 > LD1 > LD3 > LD4 > LD5

catalyzes the conversion of L-lactate to pyruvate and NADH

“Flipped pattern” indicative of MI, shock, myocarditis, or CHF

LD Peaks between 48 and 72 hours and stays elevated for 7-14 days

Liver disease increases LD4 and LD5

No clinically significant gender differences

Ranges are significantly different based upon the method used

Children have much higher LD values than adults

Hemolysis causes a gigantic spike in the LD levels

LD cannot be frozen! Activity is lost when frozen

Kidney, Liver, Muscle, and RBCs

= 52 - 236 U/L

38 - 176 U/L

CK activity is unstable and lost during storage, light sensitive

Only stable for 4 hours at RT, 48 hours at 4˚C, and 1 month at -20˚C

It doesn’t peak for 24 hours. I t’s used to assess heart attacks

It is elevated in Duchenne muscular dystrophy, seizures, trauma, and “extreme” exercise

is elevated in brain injury, and is used as a tumor marker with Prostate and Small Cell Carcinoma of the lung

travels the furthest

travelest the 2nd furthest

travels backward

Hemolysis in the tube

specific antibody against the CK-M subunit, old method and has been replaced by mass assay

- Primary anti-M antibody

Antibody attached to a solid phase,

Then a labeled secondary anti-B antibody

Signal is detected and directly proportional to CK-MB

absent or trace amount

≤6% of total CK, ≥6% is a fairly specific indicator of MI, myocardial infarction

94-100%

<3% = noncardiac source

4-5% = gray area

>6% = cardiac source

The greatest source of CK-MB in the normal serum is cardiac muscle

Catalyzes deamination

Measured by the Karmen method. Think hemolysis and hepatitis

Present in red blood cells, heart, liver, skeletal muscle, and kidney

AST is the most sensitive enzyme to alcoholic liver injury

Range at 37˚C is 5-30 U/L

No clinically significant gender differences

Hemolysis jeopardizes sample accuracy (because AST is found in high concentrations in RBCs) these are un acceptable for testing

Catalyzes the deamination

Measured by the modified Wroblewski and LaDue method

Uses Lactate Dehydrogenase as an indicator reaction

Found primarily in the cytoplasm of cells

Mostly a liver specific transaminase

DeRitis ratio (AST/ALT ratio)

Alcoholic liver disease produces a ratio >2 s = s auced and l = l osing l iver

Other hepatitis's can cause an AST/ALT ratio <1

Reference Range at 37˚C is 6-37 U/L

Hemolysis jeopardizes sample accuracy

Osteoclasts , increases in bone disease,

normal serum

Prostate is the tissue with the highest concentration

RBCs are have high intracellular concentrations

Note: can’t be performed on a hemolysed sample

Addition of tartrate inhibits Prostatic

serum is derived from osteoclasts

Hydrolase that catalyzes the hydrolysis of starches (breaks down starch into individual glucose molecules)

1.Salivary Amylase - secreted in the saliva, active at a pH of about 6.8

2.Pancreatic Amylase - secreted from the pancreas, active at the same pH

Increased in pancreatitis, alcoholism, parotitis

Macroamylasemia, not medically interesting, but can cause hyperamylasemia

SENSITIVE marker for pancreatitis

Pancreatic amylase is activated by the chloride in gastric acid

Hydrolyzes glycerol esters to produce glycerol and free fatty acids

Breaks down Triglyceride into 3 fatty acid chains and a gycerol back bone

Produced by the Pancreatic Acinar Cells

Peaks after 24 hours from the insult and remains elevated for 8-14 days

SPECIFIC marker for pancreatitis

Lipase is stable at RT for one week, 3˚C for 3 weeks, -20˚C for years

deficiency for anesthesiologists because it causes patients to remain paralyzed for a prolonged period of time after neuromuscular blocking agents are given for surgery

40-78 U/L

note :5-MNBA is measured at 410 nm

33-76 U/L

note :5-MNBA is measured at 410 nm

Tn-I or Tn-T

AST and ALT

note:ALT is more specific to liver tissue, whereas AST is found in many other tissues

GGT and LD will also increase, but they are not commonly-tested in the setting of hepatitis

• AST
• ALT

• Serum Albumin
• PT/PTT

• GGT
• ALP
• 5’-NT

Associated with gallstones (choledocholithiasis)

Refrigeration causes activity to decrease

If GGT were low, then that would rule-out a hepatobiliary source of the ALP.

Prostate Cancer

Lung, colon, ovarian, breast, uterine cancers, and lymphomas

Possibly more to come, these are the high-yield

1.Amylase

2.Lipase

If these two enzymes are not elevated, then it’s going to be hard to convince anyone that the diagnosis is pancreatitis

Competitive inhibition,

The Vmax is the same, which means
that you can overcome this type of inhibition by
increasing the substrate concentration

Note: X intercept = -1/Km, Y intercept = 1/Vmax

Noncompetitive inhibition,

The Km is the same and the Vmax is reduced, which means that there
are fewer available active binding sites for the substrate to undergo the reaction

Note: X intercept = -1/Km, Y intercept = 1/Vmax

Uncompetitive inhibition,

This inhibitor binds to the enzyme-substrate complex, therefore the reaction has a very difficult time getting going at all. Both the Km and
Vmax are affected.

Note: X intercept = -1/Km, Y intercept = 1/Vmax

Competitive inhibition

The maximum velocity can still be reached, bit the
enzyme and substrate must overcome the effects of the inhibitor, this means that it will take a higher concentration of the substrate to reach Vmax and 1/2 Vmax (or Km) will be increased

note: Asymptote = Vmax, 1/2 Vmax = Km

Noncompetitive inhibition

The maximum velocity is decreased because there are less active
sites available for the substrate to bind to undergo the reaction.
The Km will still be the same, because it will take just as much concentration of the substrate to reach 1/2 Vmax

note: Asymptote = Vmax, 1/2 Vmax = Km

Uncompetitive inhibition

This inhibitor binds to the enzyme-substrate complex, therefore the reaction has a very difficult time getting going at all. Both the Km and
Vmax are affected

note: Asymptote = Vmax, 1/2 Vmax = Km