Enzymes

Question 1

Competitive Inhibitors

Answer 1

Bind free enzyme at active site

Question 2

Noncompetitive Inhibitors

Answer 2

Binds somewhere other than the active site

Question 3

Uncompetitive Inhibitor

Answer 3

Binds to substrate

Question 4

Zero-Order Kinetics (Enzymes)

Answer 4

Large excess of substrate so that the amount of enzyme is the only rate limiting factor

Question 5

Total CK

Answer 5

Creatine Kinase

Increased in muscle, brain, or cardiac damage (CK-MB higher than 6% of total CK suggests MI)

Question 6

CK Isoenzymes

Answer 6

Two subunits, M and B
CK1: CK-BB (Brain, GI, Prostate, Uterus)
CK2: CK-MB (Cardiac)
CK3: CK-MM (Cardiac, skeletal muscle)

Question 7

LD Implications

Answer 7

Lactate Dehydrogenase

Increased in MI, Liver disease, Muscle trauma, renal infarction, Hemolytic diseases, Pernicious Anemia

Question 8

LD Testing Methods

Answer 8

Spectrophotometry

LD converts NAHD to NAD while converting pyruvate to lactate

Question 9

LD Isoenzymes

Answer 9

M and H chains, 4 subunits, 5 forms total
LD-1 and LD-2 are assoc. with Acute MI and erythrocyte destruction
LD-3: plumonary disorders, pancreatitis, amd lymphocystosis
LD-4 and LD-5 assoc. with Liver and Skeletal Muscle Disorders

Question 10

AST

Answer 10

Aspartate transaminase, found in many tissues
Highest values found in Hepatitis
Increased in MI, liver disease, muscle trauma, renal infarction, hemolysis

Question 11

ALT

Answer 11

Alanine transaminase
Highest values found in Hepatitis
Increased in liver disease, more liver specific

Question 12

GGT

Answer 12

Increased in hepatobiliary disease (especially intra- and posthepatic biliary tract obstruction), or immediately after alcohol intake
Measured spectrophotometrically

Question 13

ALP

Answer 13

Alkaline phosphatase
Optimum pH is 10, activates Mg2+
Isoenzymes are separated by electrophoresis: Regan, Placental, Intestinal, L-phenylalanine, Liver, Bone
Increased in Disorders of Bone, Hepatic Biliary Tree (highest)

Question 14

Amylase

Answer 14

In Salivary and Pancreatic Glands
Needs Ca and Cl (Should be diluted with Saline, not water)
Only enzyme normally excreted in urine
Increased: acute pancreatitis, Mumps, peptic ulcer perforation, intestinal obstruction, cholecystitis, ruptured ectopic pregnancy, mesenteric infarction, acute appendicitis

Question 15

Amylase measurement methods

Answer 15

Amyloclastic: measuring the disappearance of starch substrate
Saccharogenic: measures enzymatic action by sugar reduction
Chromolytic: measure absorbance of dye split from substrate
Enzymatic: defined substrate using coupled enzymatic reactions; can have interference from lipemia

Question 16

Lipase

Answer 16

Found in Pancreas
Elevated in Pancreatitis
Measured turbidimetrically

Question 17

ACP

Answer 17

Acid Phosphatase
Primarily from Prostate - highest elevation seen in metastasizing carcinoma of Prostate
Measured spectrophotometrically using a phosphate substrate
Specimens must be refrigerated and serum should be separated from cells as soon as possible

Question 18

Cholinesterase

Answer 18

Erythrocyte acetylcholinesterase (AChE) - True cholinesterase
Plasma acylcholine acylhydrolase (PChE) - pseudocholinesterase
Destroys acetylcholine after nerve impulse transmission
Causes of Lowered pseudocholinesterase: organophosphate poisoning, genetic susceptibility to certain anesthetics, hepatocellular disease

Question 19

CK2

Answer 19

Immunoassays measure concentration

Rises in 6-10hours, peaks in 24, drops to normal in 2-3 days

Question 20

Isoenzymes

Answer 20

Different forms of the same enzyme that perform the same catalytic function

Question 21

Cofactor

Answer 21

A non-protein compound required for enzyme activity

Question 22

Activators

Answer 22

Inorganic cofactors needed for enzymatic activity

Question 23

Coenzyme

Answer 23

Organic cofactor such as NAD

Question 24

Factors Influencing Enzymatic Reactions

Answer 24

Substrate concentration
Enzyme concentration
pH
Temp.
Inhibitors (Competitive, Noncompetitive, Uncompetitive)
pH and Temp. must remain constant for enzyme testing

Question 25

Enzyme Measurement Endpoint Methods

Answer 25

Endpoint: Reaction stops at a specified time, the product made in that time is measured
Kinetic: Measures change in absorpance at timed intervals to observe the enzyme activity

Question 26

G6PD

Answer 26

Mainly found in erythrocytes

Deficiency: inherited as X-linked trait, causing intravascular hemolysis when given anti-malarial drugs or fava beans