Enzymes Flashcards
enzyme
specific biologic proteins that catalyze biochemical reactions without altering the equilibrium point of the reaction or being consumes or changed in composition
activation energy
the energy required to raise all molecules in 1 mole of a compound at a certain temperature to the transition state at the peak of the energy barrier
apoenzyme
enzyme portion of holoenzyme (missing cofactor)
coenzyme
organic cofactor, such as NAD
cofactor
non-protein molecule necessary for an enzyme to be active
holoenzyme
complete and active system of enzyme and cofactor
enzyme-substrate complex
physical binding of a substrate to the active site of an enzyme
first order kinetics
reaction rate (binding of substrate to enzyme) is directly proportional to substrate concentration.
prosthetic group
coenzyme that is bound tightly to a enzyme
international unit
IU; amount of enzyme that will catalyze the reaction of 1 umol of substrate per minute under specified conditions
hydrolases
catalyze hydrolysis of various bonds
lyases
catalyze removal of groups from substrates without hydrolysis; the product contains double bonds
isomerases
any one of a class of enzymes that catalyze reactions involving a structural rearrangement of a molecule
kinetic assays
continuous monitoring; multiple measurements are made during the reaction, either at specific time intervals or continuously
LDH flipped pattern
An inversion of the ratio of LD isoenzymes LD1 and LD2; LD1 is a tetramer of 4 H–heart subunits, and is the predominant cardiac LD isoenzyme; it migrates more rapidly at pH of 8.6 than LD5, normally the LD1 peak is less than that of the LD2, a ratio that is inverted–flipped in 80% of AMIs within the first 48 hrs DiffDx LD flips also occur in renal infarcts, hemolysis, hypothyroidism, and gastric CA, and hemolyzed samples; LDH1 > LDH2
Michaelis-menten constant
Km; The relationship between rate of reaction and concentration of substrate depends on the affinity of the enzyme for its substrate; inverse measurement of affinity
ligases
catalyze the joining of two substrate molecules, coupled with breaking of the pyrophosphate bond in ATP or similar compound
zymogen
an inactive substance which is converted into an enzyme when activated by another enzyme.
noncompetitive inhibition
binding an enzyme at a place other than the active site and may be reversible or irreversible; slow rate of reaction; maximum velocity cannot be achieved
uncompetitive inhibition
inhibitor bind to the ES complex which will not yield product;
mixed inhibitor
binds E or ES complex at a different site from the active site
uncompetitive inhibition
inhibitor bind to the ES complex which will not yield product; increasing substrate increases inhibition
mixed inhibitor
binds E or ES complex at a different site from the active site
Immobilized enzymes
chemically bonded to adsorbents, such as agarose or certain types of cellulose, by azide groups, diazo and triazine; recoverable reagents.
Immobilized enzymes
chemically bonded to adsorbents, such as agarose or certain types of cellulose, by azide groups, diazo and triazine; recoverable reagents.
Creatine Kinase
predominant physiologic function occurs in muscle cells, where it is involved in the storage of high-energy creatine phosphate; CK levels are elevated in disorders of cardiac and skeletal muscle (myocardial infarction, rhabdomyolysis, and muscular dystrophy); extreme elevations are seen in Duchenne type muscular dystrophy
Lactate Dehydrogenase
enzyme that catalyzes the interconversion of lactic and pyruvic acids; hydrogen transfer enzyme; increased levels are found in cardiac, hepatic, skeletal, and renal disorders;
LDH-1
migrates fastest towards anode; HHHH designation; second most isoenzyme (14-26% of LDH); heart and red blood cells; Myocardial infarction, hemolytic anemia
LDH-2
major isoenzyme fraction; (29-39% of LDH); HHHM designation; heart and red blood cells; megaloblastic anemia, acute renal infarction, hemolyzed specimen
LDH-3
20-26% of LDH; HHMM designation; lung, lymphocytes, spleen, and pancreas; pulmonary embolism, pulmonary pneumonia, lymphocytosis, acute pancreatitis, carcinoma
LDH-4
8-16% of LDH; HMMM designation; liver; hepatic injury or inflammation
LDH-5
6-16 % of LDH, MMMM designation; skeletal muscle; skeletal muscle injury, muscular dystrophy
LDH-6
alcohol dehydrogenase; arteriosclerotic cardiovascular failure; signifies grave prognosis
LDH immunoglobulin complexes
LDH complexed with IgA and IgG usually migrates between LDH-3 and -4; not clinically significant
Aspartate Aminotransferase (AST)
transaminase- transfer of an amino group between aspartate and alpha-keto acids; also known as serum glutamic-oxaloacetic transaminase (SGOT or GOT); pyridoxal phosphate is a co-enzyme; used to diagnose hepatocellular disorders (i.e. viral hepatitis) and skeletal muscle involvement; in AMI levels rise within 6 to 8 hours and peak at 24 hours and return to normal within 5 days
Alanine Aminotransferase (ALT)
catalyzes the transfer of an amino group from alanine to alpha-ketoglutarate with the formation of glutamine and pyruvate; pyridoxal phosphate acts as the coenzyme; confined to evaluation of hepatic disorders; used in conjunction with AST to determine source of elevated AST
Alkaline Phosphatase (ALP)
catalyzes hydrolysis of various phosphomonoesters at alkaline pH; most useful in hepatobiliary (obstructive) and bone disorders
Acid Phosphatase (ACP)
hydrolase that catalyzes the same types of reaction as ALP but at an acid pH; indicator of prostatic cancer; used in the investigation of rape
n-glutamylltransferase (GGT)
involved in transfer of the gamma-glutamyl residue from gamma-glutamyl peptides to amino acids, water, and other small peptides; elevated in virtually all hepatobiliary disorders; may indicate alcoholism;
Amylase (AMY)
hydrolase that catalyzes breakdown of starch and glycogen; diagnosis of acute pancreatitis;
