Biochemistry Lecture 16 - Clinical Enzymology

Front 1

Enzymes and protein release in MI

Back 1

CK (creatine kinase)
Lactate DH (LDH)
CTn1 (troponin I) and cTnT (troponin T) - are cardiac specific

Front 2

Creatine Kinase (CK)

Back 2

Enzyme that catalyzes reversible conversion of creatine to creatine phosphate or phosphocreatine (CrP).
High ATP - CrP is formed
Low ATP - ATP can be formed by reverse reaction
High energy rich molecule found in cytosol and mitochondria

Front 3

Cytosolic CK

Back 3

-In serum, injury marker
-contains B and M units
-Three isozymes
-CK-BB, CK-MB, CK-MM

Front 4

CK-BB

Back 4

(CK-1) - is found mainly in brain and intestinal smooth muscle

Front 5

Heart CK, What causes increase in CK-MB serum levels?

Back 5

Consists of 30% CK-MB (Ck-2) (found only in heart)
and 70% CK-MM
Peak after 24 hours. (half life = 18 hours)
Return to baseline after few days
>3% of CK-MB of total CK indicates and increase of cTn1 or cTnT may indicate MI.

Front 6

CK-MM - What cause increased in CK-MM serum levels?

Back 6

(CK-3) - Represents 98% of total CK in skeletal muscle with about 1-2% of CK-MB.
Damage to skeletal muscle - leads to increase in CK-MM
also elevated in diseases of rhabdomyolysis or muscular dystrophy

Front 7

CK Isozymes charges

Back 7

Isozymes are negatively charged (anions)
CK-BB most negative - will travel furthest towards anode
CK-MB
CK- MM least negative

Front 8

LDH Isoenzymes:
LDH-1/2/3

Back 8

Have subunits H and M. Also markers for MI.
Normally low LDH-1/LDH2 ratio in blood. Is flipped following MI, as LDH-1 leaks from heart muscle into blood.
Peak after 48 hours.
LDH-5 - found in skeletal and liver
Peak after 48 hours.

Front 9

CTnI and CTnT

Back 9

Troponin
Not enzymes but protein found in muscle and are measured following MI. Increase as early as CK-MB, but can be measured several days after an MI when CK-MB is back to baseline.
Tropo C - not measured, not cardiac specific

Front 10

Myoglobin

Back 10

Unspecific for heart but is an early MI marker. CK-MB then peaks at 24 hours then cardiac troponin levels peak. Troponin levels are early markers which can measure after CK-MB has declined. LDH can also be measured, peak at 48 hours.

Front 11

Measuring enzymes on serum following cellular injury

Back 11

Express in x-times upper limit of normal
Mild: 2-3 times
Moderate: 2-20 times
Marked: >20 times

Front 12

Alanine and Asparate Aminotransferases (ALT and AST)

Back 12

Enzymes that are measured in serum to test for liver damage. They are not very specific. Hepatocyte may be damaged but still functioning.

Front 13

ALT

Back 13

A cytosolic enzyme, found in high amounts in liver.
Alanine from blood delivers N and C to liver, which are use in urea cycle and gluconeogenesis.

Front 14

AST

Back 14

Found in high amounts in heart and liver, found in both mitochondria and cytosol. Most liver damage results in high ALT compared to AST.
Exception: cirrhosis and ethanol abuse.

Front 15

ALP (Alkanine Phosphatase)

Back 15

Found in liver (ALP-1) (ALP-2), bone, intestine and placenta. Responsible in cleaving phosphate groups from nucleotides (DNA, RNA).
-synthesizes in cells lining bilary ducts
-obstructive processes (gall stones), induce ALP synthesis and release into serum
-Enzymes is syntehesized in osteoblasts, and involved in bone formation as it creates alkaline pH by cleaving P groups. Calcium deposit need alkaline pH.

Front 16

Intra-heaptic bile duct obstruction

Back 16

Occurs due to liver inflammation or cirrhosis.

Front 17

Extra-hepatic bile duct obstruction

Back 17

Obstructed by gallstones and tumors

Front 18

How to confirm bile duct obstruction from bone damage?

Back 18

ALP the most specific for liver, but to confirm bile duct obstruction and not ALP release from bone - test for gluatamyl transpeptidase (GGT) and conjugated bilirubin
When both GGT and ALP are high - indicates liver bile duct obstruction

Front 19

Glutathione (GSH)

Back 19

Cleaved and re-synthesized by GGT (found in liver and kidney) in cytosol of liver during active uptake of AA.
GSH is tripeptide not formed from precursor.
Peptide bond is formed using gamma- carboxyl group instead of alpha-carboxyl.

Front 20

Causes of increase of ALP-2

Back 20

ALP-2 is bone specific isozyme.
Cane be due to disease like osteomalacia or Padgets disease

Front 21

Cause of increase of GGT

Back 21

Can increase due to bile obstruction. Can also increase due to enzyme induction by ethanol.
Also caused by medical drugs. High GGT not always linked to high ALP.

Front 22

Ethanol Abuse

Back 22

Lead to increase of AST/ALT ratio >2. High GGT and lipase/amylase ration >2 - indicator of ethanol related pancreatitis.
-Leads to mitochondrial membrane damage and increased synthesis of mitochondrial AST, high AST levels result.

Front 23

Pancreatitis

Back 23

Increased level of serum amylase and increased serume lipase.
High lipase/amylase - indicates ethanol induced
Acute causes: ethanol/gallstones
Chronic: CF, hypertriacylglycerolemia

Front 24

Why is sALP normally high in children?

Back 24

ALP provides alkaline pH need for calcium deposit. Children and women during pregnancy will have high levels due to growing bones.

Front 25

How do you test for prostate cancer?

Back 25

PSA test, prostate specific antigen test

Front 26

How to test for Hepatocellular cancer and testicular and ovarian tumors?

Back 26

a-getoprotein (AFP) normally found in fetus, instead of albumin