Plasma Enzymes

Question 1

What is plasma, and how is it obtained from whole blood?

Answer 1

Plasma is the liquid component of blood obtained by separating fresh blood using an anticoagulant to prevent clotting, unlike serum, which is obtained after blood clots.

Question 2

What is Enzymology?

Answer 2

Enzymology is the study of enzymes, focusing on their structure, function, and specificity for the reactions they catalyze and their substrates.

Question 3

What is the definition of an enzyme, and what is an exception to the rule that enzymes are proteins?

Answer 3

An enzyme is a biomolecule that catalyzes specific biochemical reactions. All enzymes are proteins except ribozymes, which are RNA molecules acting as catalysts.

Question 4

What does the “-ase” suffix in enzyme names indicate?

Answer 4

The “-ase” suffix shows a molecule is an enzyme, often describing its function or substrate (e.g., amylase).

Question 5

What is an apoenzyme?

Answer 5

An apoenzyme is the protein part of an enzyme without its coenzyme, inactive until combined.

Question 6

What is a holoenzyme?

Answer 6

A holoenzyme is the complete, active enzyme with its protein part and coenzyme.

Question 7

What is an allosteric enzyme?

Answer 7

An allosteric enzyme’s substrate affinity is changed by other molecules binding at a non-active site.

Question 8

What are translocases, and their status in enzyme classification?

Answer 8

Translocases are enzymes under study, involved in molecule transport across membranes.

Question 9

How are enzymes classified by activity site?

Answer 9

Enzymes are intracellular (endoenzymes, e.g., glycogen synthase, work inside cells) or extracellular (exoenzymes, e.g., amylase, work outside cells).

Question 10

What are the two methods for measuring enzyme activity in body fluids?

Answer 10

1. Fixed time/endpoint: measures activity after stopping reaction.
2. Continuous monitoring/rate: measures absorbance at intervals to plot rate.

Question 11

How do immunoassays differ from catalytic activity measurements?

Answer 11

Immunoassays measure enzyme concentration with antibodies; catalytic measurements assess function via substrate or product changes.

Question 12

What is serial enzyme estimation, and what does it show?

Answer 12

Serial enzyme estimation tracks plasma enzyme activity over time, showing balance of entry and removal.

Question 13

What are isoenzymes, and how are they useful in diagnosis?

Answer 13

Isoenzymes are enzyme forms from different tissues (e.g., CK-MM, CK-MB). They identify the source of elevated enzyme levels.

Question 14

Why is multiple enzyme estimation useful in diagnostics?

Answer 14

It compares enzyme levels (e.g., AST vs. ALT) across tissues to identify the affected organ.

Question 15

What maintains normal plasma enzyme concentrations in healthy people?

Answer 15

Balance of synthesis, release during cell turnover, and clearance, with each enzyme having a constant half-life.

Question 16

What causes higher than normal plasma enzyme concentrations?

Answer 16

Cell proliferation, increased turnover, cell damage, enzyme synthesis induction, or reduced clearance.

Question 17

What causes lower than normal plasma enzyme concentrations?

Answer 17

Reduced synthesis, congenital deficiency, or inherited enzyme variants with low activity.

Question 18

How are enzymes used as biomarkers in clinical practice?

Answer 18

Enzymes diagnose diseases, assess prognosis, monitor therapy, support industrial uses, and evaluate drug toxicity.

Question 19

What are aminotransferases, and their role in liver disease diagnosis?

Answer 19

Aminotransferases (AST, ALT) transfer amino groups, key for diagnosing liver diseases like hepatitis.

Question 20

What is the De Ritis ratio, and how does it help in liver pathology?

Answer 20

AST/ALT ratio, normally 1.0 in serum. Higher ratio (e.g., above 2.5) indicates severe liver damage; lower suggests milder damage.

Question 21

What is Alkaline Phosphatase (ALP), and its diagnostic use?

Answer 21

ALP hydrolyzes phosphate esters at high pH, marking cholestatic liver diseases and bone disorders.

Question 22

What are the sources of ALP isoenzymes, and when do they rise naturally?

Answer 22

ALP isoenzymes come from liver, bone, placenta. They rise in pregnancy, infancy, and puberty.

Question 23

What is Gamma-glutamyl transferase (GGT), and what raises its levels?

Answer 23

GGT aids amino acid transport, elevated in cholestatic liver disease, hepatocellular damage, or drug/alcohol induction.

Question 24

What is cholestasis, and which enzymes are its markers?

Answer 24

Cholestasis is reduced bile flow from hepatocyte issues or duct obstruction. Markers are ALP and GGT.

Question 25

What are cardiac and muscle diseases linked to elevated enzyme levels?

Answer 25

Cardiac: myocardial infarction, angina. Muscle: muscular dystrophy, rhabdomyolysis.

Question 26

How does Aspartate Aminotransferase (AST) behave in myocardial infarction?

Answer 26

AST rises 12 hours after MI, peaks at 36 hours, normal by 60 hours, less specific than other tests.

Question 27

What are the isoenzymes of Lactate Dehydrogenase (LDH), and their tissues?

Answer 27

LDH isoenzymes: LD1 (H4, erythrocytes), LD2 (H3M), LD3 (H2M2), LD4 (HM3), LD5 (M4, liver, muscle). LD1/LD2 ratio is specific for MI.

Question 28

How is Creatine Kinase (CK) used as a cardiac biomarker?

Answer 28

CK isoenzymes: CK-MM (skeletal), CK-MB (cardiac), CK-BB (smooth muscle, brain). High CK-MB/total CK ratio shows cardiac damage.

Question 29

What are the isoforms of CK-MM and CK-MB, and their cause?

Answer 29

Isoforms (CK-MM1, MM2; CK-MB1–MB3) result from post-translational modifications, distinguishing cardiac from skeletal damage.

Question 30

What is the role of Amylase in diagnosing pancreatic diseases?

Answer 30

Amylase, from pancreas and salivary glands, diagnoses acute pancreatitis when elevated.

Question 31

Why is Lipase preferred over Amylase for pancreatic pathology?

Answer 31

Lipase is more specific and has a longer half-life, better for diagnosing acute pancreatitis.

Question 32

What is Acid Phosphatase (ACP), and its use in cancer diagnosis?

Answer 32

Prostatic ACP, high in prostate, monitors prostate cancer progress, less specific than PSA.

Question 33

What is Tartrate-Resistant Acid Phosphatase (TRAP), and its diagnostic use?

Answer 33

TRAP (TRAP5a, TRAP5b) hydrolyzes phosphate esters, marks metastatic bone cancers (e.g., breast, prostate).

Question 34

How does Cathepsin D aid breast cancer diagnosis?

Answer 34

Cathepsin D, a lysosomal protease, is overexpressed in breast cancer cells, aiding prognosis.

Question 35

What are Cysteine Cathepsins (CCs), and their role in cancer?

Answer 35

CCs are lysosomal proteases involved in tumorigenesis, elevated in breast, ovary, lung, and other cancers.

Question 36

What is Cyclooxygenase-2 (COX-2), and its cancer significance?

Answer 36

COX-2 converts arachidonic acid to prostaglandins, a biomarker for stomach, breast, and bladder tumors.

Question 37

How is Sorbitol Dehydrogenase (SDH) used in cancer diagnosis?

Answer 37

SDH, in liver and kidney, shows abnormal levels in prostate cancer and colorectal neoplasms.

Question 38

What are functional vs. non-functional plasma enzymes?

Answer 38

Functional enzymes have plasma roles (e.g., coagulation factors); non-functional ones are released from cells without specific plasma roles.

Question 39

How does cell damage affect plasma enzyme levels?

Answer 39

Cell damage raises enzyme levels via increased membrane permeability or cell death, releasing cytosolic proteins.

Question 40

What non-specific factors raise plasma enzyme activities?

Answer 40

Moderate exercise, intramuscular injections, drugs, alcohol (inducing GGT), or reduced clearance.

Question 41

What analytical factors affect plasma enzyme assay results?

Answer 41

Substrate, product, enzyme concentration, temperature, pH, activators, or inhibitors.

Question 42

How do non-disease factors like age, sex, race affect enzyme levels?

Answer 42

Age: higher AST in neonates, ALP in children. Sex: higher GGT/CK in men. Race: higher CK in Black people. Pregnancy raises ALP.

Question 43

What is the International Unit per litre (IU/L) for enzyme activity?

Answer 43

IU/L measures enzyme catalyzing one micromole of substrate to product per minute per liter.

Question 44

Where is Aspartate Aminotransferase (AST) found, and what raises it?

Answer 44

AST is in cardiac/skeletal muscle, liver, kidney, erythrocytes. Raised by circulatory failure, MI, hepatitis (5-10 times normal), or fatty liver.

Question 45

Where is Alanine Aminotransferase (ALT) found, and what raises it?

Answer 45

ALT is mainly in liver, less in muscle, kidney, heart. Raised by circulatory failure, hepatitis (5-10 times normal), or fatty liver.

Question 46

What conditions cause marked increases in plasma GGT activity?

Answer 46

Alcoholic hepatitis, anticonvulsant drugs, cholestatic liver disease, hypertriglyceridemia.

Question 47

What raises plasma Lactate Dehydrogenase (LDH) activity?

Answer 47

Hemolysis, circulatory failure, MI, leukemia, hepatitis, malignancy, muscle disease, pulmonary embolism, mononucleosis.

Question 48

What raises plasma Creatine Kinase (CK) activity?

Answer 48

Hemolysis, neonatal period, parturition, dermatomyositis, MI, rhabdomyolysis (5-10 times normal), muscle injury, surgery.

Question 49

What is macroamylasaemia, and how is it detected?

Answer 49

Macroamylasaemia is amylase bound to IgA, reducing renal excretion. Detected by electrophoresis or amylase/creatinine ratio below 0.02.

Question 50

How does enzyme cellular distribution affect diagnostic interpretation?

Answer 50

Cytosolic enzymes (ALT, LDH) indicate milder damage; mitochondrial/cytosolic AST suggests severe damage.