Enzymes Clinical Chemistry

what are some non-protein components of enzymes

holoenzyme (completely functional enzyme)

apoenzyme (protein portion of an enzyme)

co-factor (non-protein portion of an enzyme)

cofactors

metallic elements that help activate enzyme

• ex) iron, zinc, and magnesium

coenzyme

vitamin-derived molecules who participate directly in the reaction

• NAD and FAD

prosthetic groups

a tightly-bound non-protein portion of the enzyme

• heme

how does temperature affect the rate of a reaction?

• if too low → less enzyme-substrate binding = slower rate

  • falsely LOWERED results

• if too high → more enzyme-substrate binding = faster rate

  • falsely ELEVATED results

what are the different kinds of inhibitors

• reversible

• competitive

• non-competitive

• uncompetitive 

• irreversible

what kind of enzyme inhibition is this

•Increased Km, no change in Vmax

Competitive

what kind of enzyme inhibition is this

•Reduced Km, Reduced Vmax

uncompetitive inhibition 

what kind of enzyme inhibition is this

•No change Km, Reduced Vmax

Noncompetitive (mixed) inhibition

what is the equation for calculating international units (IU)

(absorbance/minute) x 10⁶/(a)(b) x total volume/sample volume

creatine kinase (CK)

associated with regeneration and storage of ATP

what are the 3 CKs

CK-1 : CK-BB 

CK-2 : CK-MB

CK-3 : CK-MM

•CK-BB

•Brain type

•CK 1

what can CK-BB indicate

• CVA (cerebrovascular accident)

• seizure

• nerve degeneration

•CK-MB

•Mostly found in Cardiac Muscle (Heart)

•hybrid type

•CK 2

what can CK-MB indicate

myocardial infarction (MI)

CK-MM

•Striated Muscle type

•Skeletal Muscle (rhabdomylosis)

•CK 3

what can CK-MM indicate

skeletal muscle disorders such as muscular dystrophy or crushing injury

What Kinetic method belongs to CK

Measures the NADH or NADPH at 340nm

• hexokinase & G6PDH coupling enzyme

• hemolysis will cause false increase

• cannot use EDTA, oxalate, citrate

• need non-hemolyzed serum or heparinized plasma

What Kinetic method belongs to lactate dehydrogenase (LDH/LD)

Measures the NADH or NADPH at 340nm

• pyruvate & LD coupled

what is elevated LDH associated with

• heart problems

• liver disease

• hematologic and neoplastic disorders

what are the 2 types of transaminases

Aspartate transaminase (AST)

Alanine transaminase (ALT)

aspartate aminotransferase (AST)

•Measure NADH or NADPH at 340nm. Produces oxalacetate and L-glutamate.

•Glutamic oxaloacetic transaminase is the other name.

alanine transaminase (ALT)

•Measure NADH or NADPH at 340nm. Produces oxalacetate and L-glutamate.

•Glutamic pyruvic transaminase is the other name.

alkaline phosphatase (ALP)

•Measures release of a chromogenic para-nitrophenol and inorganic phosphate at 405nm in the presence of ALP.

acid phosphatase (ACP)

•Y-glutamyl-p-nitroanilide (substrate) is used in the indicator reaction. Produces a para-nitrophenol and inorganic phosphate at 405nm in the presence of ACP.

what conditions are associates with ACP

Monitors bone disease, forensic ID of seminal body fluid, monitors prostate cancer

gamma-glutamyltransferase (GGT)

“gotta get tequila”

Y-glutamyl-p-nitroanilide (substrate) is used in the indicator reaction. It produces a p-nitroaniline at 405nm

amylase

•Measures an increase in iodine concentration from starch catabolism. Measures the disappearance or appearance of the starch or by product

lipase

•Contains a triglyceride substrate and has a choline group in it.

•Cholinesterase hydrolyzes and breaks acetylcholine into its acetate and choline components…..Acetylcholinesterase

Acetylcholinesterase or cholinesterase enzyme = Decreased levels are clinically significant in pesticide exposure

what condition is associated with ALP and LD increase?

bone disease or breakdown

what condition is associated with CK and LD increase?

•Think heart, MI

what condition is associated with •ALP, ALT, AST, LD increase?

hepatitis, think liver issues

what condition is associated with amylase increase?

acute pancreatitis or salivary gland lesions (mumps)

what condition is associated with lipase increase?

acute pancreatitis (lasts longer & more specific than amylase) 

what condition is associated with an ALP increase?

typically due to bone cancer and bone disease in general

what condition is associated with AST, ALT, ALP, LDH, ALK increase?

•hepatitis (liver associated issues)

what condition is associated with increase in lipase?

acute pancreatitis (more specific and lasts longer)

what condition is associated with an increase in amylase?

acute pancreatitis

what condition is associated with increase in CK?

•myocardial infarction, heart muscle issue