enzymes Flashcards
define enzyme
biological catalyst that increase biochemical reaction rates without undergoing permanent changes or being consumed
general equation for enzyme function
E+S->ES->E+P
define catalyst
substance that accelerates the rate of chemical reaction without becoming modified itself
define cofactos
non-protein substances that are essential for enzyme activity and must bind enzyme before rxns can happen
what is another term for inorganic cofactors
activators
list common activators
- magnesium
- chloride
- manganese
- potassium
- zinc
- calcium
define coenzymes
organic substances bound to proteins that are required for enzyme function
ture or false co enzymes are not substrates for an enzyme but participate in the reaction process
true
name a common enzyme (used in many detection assays)
NADH
define apoenzyme
protein portion of an enzyme
define haloenzyme
complete, active enzyme complex
define zymogen
inactive secreted form of enzyme
define allosteric site
a cavity other than the active site that may bid regulatory molecules
what rxn does oxidoreductase catalyze
transfer of H and O from one substrate to another
what rxn does transferase catalyze
transfer of a specific group to another
what rxn does hydrolases catalyze
hydrolysis of a substrate
what rxn does isomerases catalyze
change of the molecular form of a substrate
what rxn does lyases catalyze
non-hydrolytic removal or addition of a group to substrate
what rxn does ligases catalyze
joining of two molecules by the formation of new bonds
at what temperature are most enzymes inactivated
-5 celcius
first order kinetics
a rxn where there is constant enzyme concentration and increasing substrate concentration
in first order kinetics what is considered the rate limiting step
substrate concentration - there are open active sites remaining to be used
excess substrate can lead to the ____ phenomenon
post-zone
define zero-order kinetics
a rxn where all active sires are saturated with substrate
-> change in product concentration depends on enzyme concentration
in michaelis menten curve what is Km
the michaelis menten constant -> measure of affinity for its substrate (lower = better)
Km is the substrate concentration where rxn is at half max velocity
If the objective is to measure the enzyme activity, where on the initial velocity vs substrate concentration plot should the substrate concentration be fixed at?
zero order phase
For a technologist to successfully determine enzyme activity, which aspect of enzyme kinetics has to be overcome to determine activity?
first order
competitive inhibitors
inhibitor shares structural similarites w/ substrate and binds active site of enzyme, blocking substrate binding
non competitive inhibitors
associates with enzyme at allosteric point and allows substrate binding but prevents product formation
uncompetitive inhibitors
inhibitors binds ES complex and prevents product formation
hook effect
high concentration of enzymes, false low signal due to dilution
where is AST found
mostly in intracellular fluid - in cytoplasm and mitochondria
how is AST measured
by measuring NADH -> NAD
ALT
- distributed in liver and kidneys
- greater specificity for damaged liver tissue
- found only in cytoplasm
how is ALT measured
NADH-> NAD
in AST assay what is oxaloacetate reduced to
malate by malate dehydrogenase
in ALT assay what is oxaloacetate reduced to
lactate by lactate dehydrogenase
What does ALP catalyze
hydrolysis of substrates at alkaline pH
true or false ALP has many isoforms including ones for the liver, bone and placenta
true, liver isozenyme most conentrated
what diseases are associated with ALP
obstructive hepatobiliary disease
osteoblast mediated bone disease
what are the main pancreatic enzymes
lipase - fat removal (injury diagnosis)
amylase - sugar removal (injury indicator)
protease - proteins
S-amylase
secreted by salivary glands to digest sugar, deactivated in stomach
P-amylase
secreted by acinar cells into the stomach to break down sugars once content reaches stomach
lipase
only test needed in diagnosis of acute pancreatitis (enzyme exclusive to pancreas)
what activators does lipase need
colipase in presence of bile salts
creatine kinase
catalyzes reversible phosphorylation of creatine to creatine phosphate (energy usage)
most common disease associated with increased lvls of CK
acute myocardial infraction (CK-MB)
this is an energy source utilized by muscles
creatine phosphate
enzyme historically used to assess prostate health before replacement by PSA
acid phosphatase
