Enzymes (8.1-8.26)

enzyme

protein that decreases the activation energy of a reaction and isn’t consumed

catalyst

increases the reaction rate without being permanently changed

apoenzyme

protein part that requires cofactor to activate

coenzyme/cofactor

non protein part that is essential for the reaction

active site

specific location where the reaction takes place

substrate

substance that is used up in the reaction

product

substance that is formed in the reaction

inhibitor

substance that prevents reaction

kinetic assay

change in absorbance is measured on a spectrophotometer to see reaction rate

international unit

unit of activity for substances defined in terms of the activity of a standard solution

Vmax

maximum velocity of an enzymatic reaction

Km

concentration of substrate which lets enzyme reach HALF of Vmax

activation energy

energy required to start reaction

first order reaction

reaction rate dependent on substrate and enzyme concentrations

zero order reaction

reaction rate is constant on dependent on only enzyme concentration

Lineweaver Burk plot

graphs of the reciprocals of substrate concentrations on x and reaction velocity concentrations on y

Michaelis-Menten constant

substrate concentration when the reaction rate is half of Vmax

affinity of enzymes to its substrate

enzymes with lower Km values have higher affinity

Km

Michaelis-Menten Constant

competitive inhibitor

same Vmax, different Km, can be overcome by increasing substrate concentration to drown out inhibitor

First order kinetics

1 to 1 relationship between substrate and velocity

non competitive inhibitor

same Km, different Vmax, binds to different enzyme sites, making them ineffective, decreasing amount of active enzymes drops Vmax

zero order kinetics

reaction rate reaches asymptote, all enzymes are taken and the velocity cannot be changed by adding more substrate

Lactate dehydrogenase

vital enzyme for energy production, catalyzes conversion of L-lactate to pyruvate and NADH

LD-1 (HHHH) tissues

Heart, RBCs, Kidneys

LD-2 (HHHM) tissues

Lungs, RBCs

LD-3 (HHMM) tissues

spleen, lungs, many tissues

LD-4 (HMMM) tissues

liver and skeleton, same as LD-5

LD-5 (MMMM) tissues

liver and skeleton, same as LD-4

LD pathology

LD2 > LD1 > LD3 > LD4 > LD5

2 methods for and LD isoenzyme panel

wacker procedure + wroblewski and Ladue reaction

Wacker procedure

L-lactate + NAD+ = pyruvate + NADH + H+ opposite of wroblewski

wroblewski and ladue reaction

pyruvate + NADH + H+ = L-lactate + NAD+; preferred, cheaper, and oppsite of wroblewski

creatine kinase tissue source

heart, skeleton, small amounts in brain

CK-MB

Myocardial band, heart attack, critical timing as it doesn’t peak for 24 hours

CK-MM

skeletal muscle, elevated in duchenne muscular dystrophy, seizures, trauma, and extreme exercise

creatine kinase pathology

CK-BB

Brain tissue, brain injuries and seres as a tumor marker with prostate and small cell carcinoma of the lungs

CK results

CKBB travels farthest up electrophoresis, CKMM travels backwards

CK isoenzymes

Anti-CKB binds only to CKM and is proportional to CKMB

Aspartate Aminotranserferase AST

RBCs, heart, liver, kidney, most sensitive enzyme to alcoholic liver disease

Alanine Aminotransferwase ALT

mostly liver specific, hepatitis

Gamma Glutamyl Transferase GGT

biliary tract, intestines, liver, helps differentiate hepatobiliary disorders

Acid Phosphatase ACP

prostate, RBCs, prostate cancer

Amylase AMS

two types, salivary from spit and pancreatic, sensitive to pancreatitis,

Lipase LIP

pancreas, hydrolyzed glycerol esters, specific for pancreatitis

LIP assays

turbidimetric and enzymatic, stable for 1 week

pancreatitis enzymes

AMS is sensitive, LIP is specific, AMS will increase in other tests besides pancreatitis

cholinesterase CHE

RBCs, lungs, spleen, CNS, AChE deficiency can cause prolonged paralysis

associations with Myocardial Infarction

Troponin 1 and troponin T

enzyme associations with Hepatitis

AST and ALT both increase, ALT is specific to liver, GGT and LD also increase but are supplementary

enzyme associations with Bone Disease

Alkaline Phosphatase ALP, in bone and biliary tract, gallstones and refrigeration causes activity decline

enzyme associations with Malignancy

ACP for prostate cancer, ALP for lung, colon, ovarian, breast cancers

enzyme associations with Pancreatitis

Amylase and lipase

enzyme associations with hemolytic anemia

ACP, AST, LD

Discuss advances in the detection of prostate cancer

prostate specific antigen PSA can give false positives but is sensitive to detecting prostate cancer