CC2 Enzymes - Feb 26 quiz Flashcards
6 Enzyme Classes
Class 1 Oxidoreductases
Class 2 Transferases
Class 3 Hydrolases
Class 4 Lyases
Class 5 Isomerases
Class 6 Ligases
ENZYME NOMENCLATURE consisting of 4 numbers separated by periods
Enzyme class
subclass
Sub-subclass
Serial number for substrate
Enzymes follow the ___ kinetics
Michaelis-Menten
Enzymes undergo function as governed by two theories
Fischer’s Lock and Key theory
Koshland’s Induced Fit theory
theory….enzyme (lock) and substrate (key) perfectly fits
Fischer’s Lock and Key theory
theory ….enzyme undergoes conformational changes to accommodate shape of the substrate
Koshland’s Induced Fit theory
factors affecting enzymes (7)
substrate concentration,
enzyme concentration,
pH,
temperature,
cofactors,
inhibitors
Types of Enzyme Assay (3)
● Endpoint Analysis
● Multipoint Assay
● Kinetic Assay
✅● Endpoint Analysis
= reaction is initiated by the addition of substrate
and allowed to proceed for a period of time
= measurement of the product or substrate is done at the end of the reaction
✅ ● Multipoint Assay
= measures the change in concentration of the substance at several intervals during the course of the assay
✅ ● Kinetic Assay
= continuous measurement of change in concentration as a function of time
ENZYME INHIBITION (4)
✅No inhibition – Absence of inhibitor
✅Competitive – inhibitor binds to ACTIVE SITE
✅Noncompetitive – inhibitor binds to ALLOSTERIC SITE
✅Uncompetitive– inhibitor binds to E-S COMPLEX
interpret… CK-MB present and LD
both MI and non MI cases
interpret… CK-MB present and flipped LD
100% predictive value that there is MI
(4) Pronounced elevation of CK (5 or more times normal)
● Duchenne’s muscular dystrophy
● polymyositis
● dermatomyositis
● AMI
Mild or moderate elevation (2-4 times Normal)
● severe exercise, trauma, surgical procedure, IM injections
● delirium tremens, alcoholic myopathy
● MI, severe iochemic injury
● pulmonary infarction
● pulmonary edema
● hypothyroidism
● acute agitated psychoses
Reversible conversion of lactate to pyruvate using NAD+ as cofactor
LACTATE DEHYDROGENASE
LD class heart, brain, RBC
LD1 and LD2
LD class brain kidney lung
LD3
LD class liver, skeletal muscle, kidney
LD4 and LD5
LD Pronounced Elevation (5 or more times Normal)
● Megaloblastic anemia
● Widespread carcinomatosis, esp. hepatic metastases
● Septic shock and hypoxia
● Hepatitis
● Renal infarction
● Thrombotic thrombocytompenic purpura
LD Moderate Elevation (3-5 times Normal)
● MI
● Pulmonary infarction
● Hemolytic conditions
● Leukemia
● IM
● Delirium tremens
——- (a psychotic condition typical of withdrawal in chronic alcoholics, involving tremors, hallucinations, anxiety, and disorientation)
● Muscular dystrophy
LD Slight Elevation (Up to 3 times Normal)
● Most liver diseases
● Nephrotic syndrome ● Hypothyroidism
● Cholongitis
NOTE : Association of LD1 & LD2 is useful in confirming diagnosis
of MI after CK has returned to normal (LD flipped) Note: hemolysis should be absent
NOTE : Association of LD1 & LD2 is useful in confirming diagnosis of MI after CK has returned to normal (LD flipped) Note: hemolysis should be absent
● first protein marker to diffuse out of ischemic muscle cells
● presumptive for AMI (not specific, only sensitive)
MYOGLOBIN
troponin polypeptides … released into circulation following myocardial injury (highly specific)
I & T released into circulation following myocardial injury (highly specific)
✅ skeletal muscles have different troponins
✅ peaks at 4-8 hours; fresh appearance in serum suggests AMI
● Act on compounds with single PO4 groups
● has orthophosphate ester monohydrolase activity
● optimally active at pH 5 (acid phosphatase) most active at pH 9 (alkaline phosphatase)
PHOSPHATASES
major enzyme in detecting prostatic cancer
Prostatic ACP
✅ medicolegal evaluation of rape- vaginal swab during pelvic exam; replaced DNA testing
● high in bone, liver, intestine, kidney, WBCs & placenta
● Placenta ● intestine
● germ cell & lung
● bone, liver, kidney, granulocytes
ALP
most common method of distinguishing ALP isoenzymes
heat fractionation
✅ (serum heated at 56OC for 15 min. & assayed for remaining ALP activity)
Bone ALP elevation in cases of
osteoblastic growth responses,
healing bones,
Paget’s disease,
bone CA,
myeloma,
rickets,
hyperparathyroidism
osteomalacia
The placenta oncofetal form of ALP
✅ Regan isoenzyme
blood type ___ and ____secretory status- secrete intestinal ALP into circulation after a meal
O & B
specific marker released from lymphocytes during HIV infection in children
ALP (band 10)-
ALP Pronounced elevations (5 or more time Normal)
Bile duct obstruction (intrahepatic or extra)
Biliary cirrhosis
Paget’s disease
Osteogenic sarcoma Hyperparathyroidism
✅Moderate elevation (3-5 times Normal)
Granulomatous or infiltration dses of liver
IM
Metastatic tumor in bone
Metabolic bone disease (rickets, osteomalacia)
✅ Slight elevation (up to 3 times Normal)
Viral hepatitis
Cirrhosis (intestinal isoenzyme often present Healing fractures
Pregnancy (placental isoenzyme) Normal growth patterns in children
CONDITIONS IN WHICH THE SERUM ALP IS INCREASED (5)
Healing fractures
Biliary cirrhosis
Rickets
Osteoporosis
Bone cancer
Enzyme that finds out the severity of inflammatory muscle dx….
Glycolytic enzyme that splits fructose- 1,6 diphosphate into two triose phosphate molecules in the metabolism of glucose
ALDOLASE
Catalyze the reversible transfer of an amino group between an amino acid and an alpha-keto acid
AMINOTRANSFERASES
2 AMINOTRANSFERASES
ALT
AST
large amount in liver, myocardium & skeletal
muscle; moderate in RBCs
AST
specimens for amylase
Urine
Serum
Saliva
Pleural fluid
Peritoneal fluid
✅diastase
✅ found in salivary glands & pancreas
Insecticide poisoning & Nephrotic syndrome
CHOLINESTERASE
Note:
ANGIOTENSIN-CONVERTING ENZYME
: bp regulation
Produced in the lungs by macrophages & epithelioid cells
✅ Primary diagnostic use is for active sarcoidosis
✅ used to evaluate active granulomatous pulmonary dse
ANGIOTENSIN-CONVERTING ENZYME
GGT clinical significance
✅ obstructive jaundice
✅ metastatic liver cancer
✅ intrahepatic cholestasis
discuss how to differentiate Bone and Liver cancer using GGT and ALP…..which enzyme is elevated?
-
Lysozyme/Muramidase elevated in
**In serum:
**✅ Acute monocytic leukemia
✅ Acute myelomonocytic leukemia
**found in
**✅ tears
✅ saliva
✅ sputum
✅ also granulocytes & monocytes
📝
Liver————– AST
Heart ———— CK-MB
Skeletal Muscle ———CK-MM
Bone ——- ALP (heat labile)
Prostate ———– ACP
Pancreas ———— AMS
Brain ————– CK-BB
specificity of enzymes
Absolute
Bond
Group
Stereospecificity
features of coenzymes
- Transfer a functional group
- Essential for enzyme activity
- Heat stable low MW organic substance
- Combines loosely with apoenzyme
- Can be separated from apoenzyme via dialysis
Factors that affect enzymatic activity
- [H*]
- Activators
- Inhibitors
- Enzyme concentration
- Substrate concentration
Enzymes composed wholly of protein are known as
simple enzymes
enzymes which are composed of protein plus a relatively small organic molecule.
complex enzymes aka Holoenzymes
the protein component of enzyme…. while the non protein??
apoenzyme
Coenzyme or prosthetic group (non protein)
four possible mechanisms of catalysis
- Catalysis b yBond Strain
- Catalysis by Proximity and Orientation
- Catalysis Involving Proton Donors (Acids) and Acceptors (Bases)
- Covalent Catalysis
Draw the Fischer’s Lock & Key Model
….
Changes in pH &temperature affect the…
Tertiary structure
Noncovalent forces
change their structure in response to binding of effectors.
Allosteric enzymes
Thiamine coenzyme
TPP
Riboflavin coenzyme
FMN, FAD
Competitive inhibitors bind reversibly to the enzyme, preventing the binding of substrate. On the other hand, binding of substrate prevents binding of the inhibitor. Substrate and inhibitor compete for the enzyme.
Competitive inhibition
In uncompetitive inhibition the inhibitor can not bind to the free enzyme, but only to the ES-complex.
Uncompetitive inhibition
Non-competitive inhibitors can bind to the enzyme at the same time as the substrate, i.e. they never bind to the active site.
Non-competitive inhibition
This type of inhibition resembles the non- competitive, except that the EIS-complex has residual enzymatic activity.
Mixed inhibition
🫴🐈
✅ Competitive Inhibitor
* Specifically at the catalytic site, where it competes with substrate for binding in a dynamic equilibrium- like process.
* Inhibition is reversible by substrate.
* Vmax is unchanged; Km, as defined by [S] required for 1/2 maximal activity, is increased.
✅ Noncompetitive Inhibitor
* Binds E or ES complex other than at the catalytic site. Substrate binding unaltered, but ESI complex cannot form products.
* Inhibition cannot be reversed by substrate
* Km appears unaltered; Vmax is decreased proportionately to inhibitor concentration.
✅ Uncompetitive Inhibitor
Binds only to ES complexes at locations other than the catalytic site.
* Substrate binding modifies enzyme structure, making inhibitor- binding site available.
* Inhibition cannot be reversed by substrate.
* Apparent Vmax decreased; Km, as defined by [S] required for 1/2 maximal activity, is decreased.Note
