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Flashcards in Enzymes Deck (26)
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1

Competitive Inhibitors

Bind free enzyme at active site

2

Noncompetitive Inhibitors

Binds somewhere other than the active site

3

Uncompetitive Inhibitor

Binds to substrate

4

Zero-Order Kinetics (Enzymes)

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

5

Total CK

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

6

CK Isoenzymes

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

7

LD Implications

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

8

LD Testing Methods

Spectrophotometry
LD converts NAHD to NAD while converting pyruvate to lactate

9

LD Isoenzymes

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

10

AST

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

11

ALT

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

12

GGT

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

13

ALP

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)

14

Amylase

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

15

Amylase measurement methods

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

16

Lipase

Found in Pancreas
Elevated in Pancreatitis
Measured turbidimetrically

17

ACP

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

18

Cholinesterase

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

19

CK2

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

20

Isoenzymes

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

21

Cofactor

A non-protein compound required for enzyme activity

22

Activators

Inorganic cofactors needed for enzymatic activity

23

Coenzyme

Organic cofactor such as NAD

24

Factors Influencing Enzymatic Reactions

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

25

Enzyme Measurement Endpoint Methods

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

26

G6PD

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