(4) Enzymes Flashcards
Enzymes are protein catalysts involved in the regulation of…
biochemical reactions in metabolic pathways.
Enzymes increase…
the rate of reaction without being altered or consumed during a reaction.
Enzymes ___ the activation energy of a reaction.
Lower.
Role of oxidoreductases.
Catalyze oxidation-reduction reactions.
Role of transferases.
Catalyze group transfer of C, N, or P containing groups.
Role of hydrolases.
Catalyze cleavage bonds by the addition of water.
Role of lyases.
Catalyze cleavage of C-C, C-S, & certain C-N bonds, lysis generating a double bond.
Role of isomerases.
Catalyze optical or geometric isomers, rearrangements.
Role of ligases.
Catalyze the formation of bonds between C, O, S, N; coupled of hydrolysis of high energy phosphates (ATP required).
Reference range of AST.
5 - 30 U/L.
Reference range of ALT.
6 - 37 U/L.
Reference range of CPK.
15 - 160 U/L (slightly lower in females).
Reference range of GGT.
6 - 45 U/L (slightly lower for females).
Reference range of LDH.
Forward: 100-225 U/L.
Reverse: 80 - 290 U/L.
Reference range of ALP.
30 - 90 U/L.
Reference range of AMY.
95 - 290 U/L.
State the enzyme class for each of the following analytes:
AST, ALT, CK, GGT
Transferases.
State the enzyme class for each of the following analytes:
LDH, G-6-PD
Oxidoreductase.
State the enzyme class for each of the following analytes:
PChE, AMY, LIP, ALP, ACP
Hydrolases
State the enzyme class for each of the following analytes:
ALD
Lyase.
State the optimal pH for the following analyte:
Amylase
6.9 - 7.0
State the optimal pH for the following analyte:
ALP
10
State the optimal pH for the following analyte:
ACP
5.0
State the optimal pH for the following analyte:
Lipase
8.6 - 9.0
State the cofactors required for the following analyte:
CPK
Mg2+
State the cofactors required for the following analyte:
Lipase
Colipase
State the cofactors required for the following analyte:
Amylase
Calcium and Chloride
State the cofactors required for the following analyte:
ALP
Mg2+, CO2+, Mn2+
State the cofactors required for the following analyte:
LD
NAD+
Explain Kinetic measurement.
Measures the concentration continuously throughout the reaction.
Explain End point measurement.
Measures enzyme concentration by measuring a substance after the reaction is stopped (fixed time method).
Define the international unit and how it applies to enzymes.
Enzyme activity rather than concentration is measured in serum or plasma. A unit of activity is expressed as IU which is a standard unit established for all methods.
In enzyme testing, 1 IU is that quantity of enzyme that will…
catalyze the reaction of one micromole of substance per minute under optimum reaction conditions.
Explain zero order kinetics.
The reaction is independent of substrate concentration.
Explain first-order kinetics.
Reaction velocity is directly proportional to substrate concentration.
Explain competitive inhibition.
Inhibitor similar to the normal substrate molecule competes with the substrate for binding at the activation site.
KM increases, Vmax no change
Explain noncompetitive inhibition.
Inhibitor binds to enzyme at a site other than the active site.
KM no change, Vmax decreases
Explain uncompetitive inhibition.
Inhibitor binds to the ES complex and prevents product formation
KM decreases, Vmax decreases
List the main tissue source for the following enzyme:
AST
Liver, myocardial, skeletal muscle, kidney.
List the main tissue source for the following enzyme:
ALT
Liver, skeletal muscle, kidney, heart, pancreas, lungs, spleen erythrocytes.
List the main tissue source for the following enzyme:
CPK
Skeletal muscle, brain, stomach muscles.
List the main tissue source for the following enzyme:
GGT
Kidney, liver, pancreas, and intestine.
List the main tissue source for the following enzyme:
LDH
Brain, erythrocytes, WBC, kidneys, liver.
List the main tissue source for the following enzyme:
Lipase
Pancreas (only one of clinical significance), intestinal mucosa, leukocytes, and adipose tissue.
List the main tissue source for the following enzyme:
Amylase
Salivary glands and acinar cells of pancreas.
List the main tissue source for the following enzyme:
ACP
Greatest concentration in prostate, liver, kidneys, erythrocytes, platelets, bone.
List the main tissue source for the following enzyme:
ALP
Liver, bone, placenta, intestine, spleen, and kidneys.
State the most prominent location(s) for the following LDH isoenzyme:
LD1 (HHHH)
Heart, RBCs.
State the most prominent location(s) for the following LDH isoenzyme:
LD2 (HHHM)
Renal cortex.
State the most prominent location(s) for the following LDH isoenzyme:
LD3 (HHMM)
Lung, spleen, pancreas, lymphocytes.
State the most prominent location(s) for the following LDH isoenzyme:
LD4 (HMMM)
Liver, skeletal muscle.
State the most prominent location(s) for the following LDH isoenzyme:
LD5 (MMMM)
Liver, skeletal muscle.
What are the possible disease states for the following serum enzyme elevations:
CK
- MI,
- muscle disorders,
- cerebrovascular accidents,
- CO poisoning,
- after shock or circulatory failure.
What are the possible disease states for the following serum enzyme elevations:
LD
- Pernicious anemia,
- MI,
- pulmonary disorders,
- hepatitis,
- skeletal disorders.
What are the possible disease states for the following serum enzyme elevations:
AST
- MI,
- liver disease,
- muscular dystrophy.
What are the possible disease states for the following serum enzyme elevations:
ALT
- Hepatic disorders,
- Increased ALT specific for liver disease,
- viral hepatitis.
What are the possible disease states for the following serum enzyme elevations:
ALP
- Hepatobiliary disorders (obstruction)
- Bone diseases
- Pregnancy
- Carcinomas
What are the possible disease states for the following serum enzyme elevations:
ACP
- Prostate cancer
- Bone disease
- Thrombocytopenia
What are the possible disease states for the following serum enzyme elevations:
GGT
- Alcoholism
- Hepatobiliary Disorders
What are the possible disease states for the following serum enzyme elevations:
AMS
- Acute pancreatitis
- Mumps
- Perforated ulcer
- Acute appendicitis
- Macroamylasemia
- AIDS
What are the possible disease states for the following serum enzyme elevations:
LPS
- Pancreatitis
- Ulcers
- Intestinal obstruction
What are the possible disease states for the following serum enzyme elevations:
5’-nucleatidase
- Hepatobiliary
Relate pathologic conditions with an enzyme increase and the degree of elevation:
Metastatic Carcinoma of Prostate
Increased: acid phosphatase
Relate pathologic conditions with an enzyme increase and the degree of elevation:
Myocardial Infarction
Increased: CK, CK-MB, LD, AST
Relate pathologic conditions with an enzyme increase and the degree of elevation:
Hepatocelular Disease
Increased: ALP, GGT, AST, ALT, 5’-nucleotidase
Relate pathologic conditions with an enzyme increase and the degree of elevation:
Pancreatic Disease
Increased: lipase, amylase
Relate pathologic conditions with an enzyme increase and the degree of elevation:
Bone Disease
Increased: ALP, ACP
Relate pathologic conditions with an enzyme increase and the degree of elevation:
Muscle Disease
Increased: CK, aldolase, AST, LD
Relate pathologic conditions with an enzyme increase and the degree of elevation:
Malignancy
Increased: LD (moderate leukemia, hemolysis), GGT
Relate pathologic conditions with an enzyme increase and the degree of elevation:
Alcoholism
Increased: GGT (occult alcohol intake)
Relate pathologic conditions with an enzyme increase and the degree of elevation:
Obstructive Jaundice
Increased: GGT, ALP
Relate pathologic conditions with an enzyme increase and the degree of elevation:
Hepatitis, acute and chronic
Increased: AST and ALT, 100x higher elevations in acute vs. chronic
Indicate the percentage of the distribution of CK isoenzyme in the following human tissues:
Normal Serum
CKMM: 100%
Indicate the percentage of the distribution of CK isoenzyme in the following human tissues:
Skeletal Muscle
CKMM: 100%
Indicate the percentage of the distribution of CK isoenzyme in the following human tissues:
Heart
- *CKMB**: 40%
- *CKMM**: 60%
Indicate the percentage of the distribution of CK isoenzyme in the following human tissues:
Brain
- *CKBB**: 90%
- *CKMM**: 10%
Indicate the percentage of the distribution of CK isoenzyme in the following human tissues:
Lung
- *CKBB**: 90%
- *CKMM**: 10%
Indicate the percentage of the distribution of CK isoenzyme in the following human tissues:
Bladder
- *CKBB**: 95%
- *CKMM**: 5%
Indicate the percentage of the distribution of CK isoenzyme in the following human tissues:
Bowel
CKBB: 100%
During a myocardial injury determine the when elevation is apparent, when they peak, and how long it takes for these analytes to return to normal:
CK
- *Time of Elevation**: 4 - 8 hours
- *Peak**: 12 - 24 hours
- *Return to Normal**: 3 - 4 days
During a myocardial injury determine the when elevation is apparent, when they peak, and how long it takes for these analytes to return to normal:
LD
- *Time of Elevation**: 12 - 24 hours
- *Peak**: 48 - 72 hours
- *Return to Normal**: 5 - 10 days
During a myocardial injury determine the when elevation is apparent, when they peak, and how long it takes for these analytes to return to normal:
AST
- *Time of Elevation**: 6 - 8hrs
- *Peak** 24hrs
- *Return to Normal**: 3 - 5 days
During a myocardial injury determine the when elevation is apparent, when they peak, and how long it takes for these analytes to return to normal:
Troponin (I)
- *Time of Elevation**: 2 - 6hrs
- *Peak**: 13 - 30hrs
- *Return to Normal**: 7 days
During a myocardial injury determine the when elevation is apparent, when they peak, and how long it takes for these analytes to return to normal:
Myoglobin
- *Time of Elevation**: 2 - 5hrs
- *Peak**: 2hrs
- *Return to Normal**: 24hrs
Which cardiac marker is first to show elevation following a myocardial injury?
Myglobin.
What is the significance of the CK relative index (CKI)?
The CKI is an expression of the percentage of the total CK that is attributed to CKMB.
Normal reference range of CKI.
0 - 4%
CKI values greater than 4% are indicative of…
CKMB increase due to cardiac muscle (i.e. myocardial infarction).
Calculate the CK relative index when the total CK = 735 U/L and the CKMB = 23 ug/L.
CKI = (CKMB ug/L)/(Total CK) x100
=23/735 x100
= 3.1%
(T/F) Increases in CK and CKMB probably not due to myocardial infarction.
True.
What is the clinical usefulness of Troponin?
Troponin is a complex protein of three subunits C, T, and I.
When heart damage occurs, they are released into circulation.
What are the troponin assays?
- Quantitative monoclonal immunoassay
- Qualitative immunoassay
What analyte is replacing troponin and why?
Due to their specificity and sensitivity, they are being replaced by the use of CK-MB.
What are lipases?
Enzymes that hydrolyze the ester linkage of fats to produce alcohols & fatty acids.
Why test for lipase levels?
Since acinar cells of the pancreas produce it predominantly, it is useful in diagnosing acute pancreatitis.
How does EDTA affect lipase values?
Decreases activity of lipase, causing falsely decreased results.
Relate lipase and amylase results in acute pancreatitis and acute appendicitis.
Acute Pancreatitis: increased lipase and amylase; hyperlipidemia may suppress lipase resulting in a false normal amount.
Opiates and morphine administered for pain before drawing sample will give a false elevation.
Acute Appendicitis: increased amylase, usually normal lipase.
List the amylase isoenzymes.
- *P-AMS (Pancreatic)**: P1, P2, and P3
- *S-AMS (Salivary)**: S1, S2, S3
What would an increased urine amylase suggest?
Acute pancreatitis, peptic ulcer, intestinal obstruction.
What would be an increased serum amylase without an increase in urine indicate?
Benign Macroamylasemia
Enzyme bound to an immunoglobulin or other substance resulting in an unexplained persistent increase in serum.
What might GGT increase in myocardial infarction?
Occurs when there is hypoxic liver damage from circulatory disturbances.
When is elevated ALP seen under normal physiological conditions?
Pregnancy and bone growth due to normal growth or healing fractures.
Explain elevated alkaline phosphatase in children and pregnancy.
ALP is increased in children due to the increased osteoblastic activity during bone growth. ALP increases between labor 16th and 20th weeks of pregnancy until labor. (Placental ALP).
What fraction of the ALP enzyme is the most heat stable?
Placenta.
Assess the effect of insecticide poisoning on cholinesterase level and the most common method for measurement.
Some organophosphorus compounds found in many insecticides decrease pseudocholinesterase (PChE) activity.
Inhibition of PChE is characterized by tremors and paralysis.
Acylthiocholine esters are used as substrates; activity of PChE is determined from the rate of hydrolysis of butyryl or propionyl thiocholine in the presence of a chromogenic disulfide agent.
What enzymes will be affected by slight hemolysis?
LD.
What enzymes will be affected by moderate hemolysis?
LD, ALP, amylase, ALT, AST, ACP.
Does hemolysis interfere with ALT?
Yes.
Determine the products of the following reaction:
Creatinine + ATP
Creatinine Phosphate + ADP
Determine the products of the following reaction:
Lactate + NAD+
Pyruvate + NADH + H
Determine the products of the following reaction:
Aspartate + Alpha Ketoglutarate
Oxaloacetate + Glutamate
Determine the products of the following reaction:
Alanine + Alpha Ketoglutarate
Pyruvate + Glutamate
Determine the products of the following reaction:
Phosphomonoester + H2O
Alcohol + Phosphate ion
Determine the products of the following reaction:
Glutathione + Amino Acid
Glutamyl-peptide + L-cysteinyl glycine
Determine the products of the following reaction:
Triglyceride + 2 H2O
2-monoglyceride + 2 fatty acid