Enzymes: Transferases

Question 0

Once the alpha-ketoglutarate accepts the amine group, what is it converted to?

Answer 0

L-glutamate

Question 1

What reaction do the aminotransferases catalyze?

Answer 1

The transfer of an amine group to an alpha-ketoglutarate.

Question 2

What varies for each aminotransferase when the amino acid is donated?

Answer 2

The amino acid substrate that donates the amine group

Question 3

What is required to transfer the amine group to alpha-ketoglutarate?

Answer 3

Pyridoxal-5-phosphate

Question 4

What other name is pyridoxal-5-phosphate known as?

Answer 4

Vitamin B6

Question 5

What does AST stand for?

Answer 5

Aspartate aminotransferase

Question 7

What does ALT stand for?

Answer 7

Alanine aminotransferase

Question 8

What is the pH optimum for AST and ALT?

Answer 8

7.3-7.8

Question 9

How long is AST stable when refrigerated?

Answer 9

3-4 days

Question 10

What reaction does AST catalyze?

Answer 10

The amine transfer from aspartic acid to alpha-ketoglutarate

Question 11

What are the products formed when AST catalyzes a reaction?

Answer 11

Oxaloacetate and L-glutamate

Question 12

Does hemolysis affect AST measurement?

Answer 12

Yes, it falsely increases AST activity due to AST being present in RBCs.

Question 13

Where is AST found in highest concentrations?

Answer 13

Heart, liver, skeletal muscle

Question 14

Where is AST found in smaller amounts?

Answer 14

Kidney, pancreas, spleen, lung, RBC

Question 15

In what disease states is an elevated AST seen in?

Answer 15

Heart disease, liver disease, skeletal muscle disorders, pulmonary embolism, acute pancreatitis

Question 16

Is an elevated AST diagnostic for an AMI?

Answer 16

No, it has limited diagnostic use due to it taking too long to increase (6-8 hours after pain onset).

Question 17

In viral hepatitis, how many times the URL will AST be increased?

Answer 17

30-50x the URL

Question 18

In toxic hepatitis, how many times the URL will AST be increased?

Answer 18

As high as 100x the URL

Question 19

What reaction does ALT catalyze?

Answer 19

The transfer of an amine group on alanine to alpha-ketoglutarate

Question 20

What products are formed in the reaction ALT catalyzes?

Answer 20

Pyruvate and glutamate

Question 21

How long is ALT stable at refrigerated temperature?

Answer 21

3-4 days

Question 22

Is ALT measurement affected by hemolysis?

Answer 22

No

Question 23

Where is ALT found in highest concentration?

Answer 23

Liver

Question 24

Where else can ALT be found in the body?

Answer 24

Widely distributed through the body in small amounts (heart, kidney, skeletal muscle)

Question 25

In what disease states is ALT elevated in?

Answer 25

Liver disease (viral/toxic hepatitis, cirrhosis, hepatic obstructive disorders)

Question 26

In what disease state will ALT be higher than AST?

Answer 26

Acute inflammatory process (like hepatitis)

Question 27

In what disease state will AST be higher than ALT?

Answer 27

Severe liver necrosis (cirrhosis and hepatocellular carcinoma)

Question 28

Why is AST higher than ALT in severe liver necrosis?

Answer 28

Mitochondrial AST is stored in RBCs and as scar tissue replaces living tissue, AST is released from the RBCs, leading to the elevated levels?

Question 29

What is the difference between ALT and AST measurement?

Answer 29

Each utilize a different substrate

Question 30

What are the substrates used for AST measurement?

Answer 30

Alpha-ketoglutarate and aspartate

Question 31

What are the substrates used for ALT measurement?

Answer 31

Alpha-ketoglutarate and alanine

Question 32

What is the name of the method used to measure ALT and AST?

Answer 32

Karmen method

Question 33

What is actually measured in the Karmen method?

Answer 33

As NADH is converted to NAD, a decrease in absorbance at 340 nm is observed which is proportional to AST activity

Question 34

In the measurement of AST, what enzyme is used to catalyze the conversion of oxaloacetate to malate?

Answer 34

Malate dehydrogenase

Question 35

What does GGT stand for?

Answer 35

Gamma-glutamyltransferase

Question 36

What reaction does GGT catalyze?

Answer 36

Catalyzes the transfer of a gamma-glutamyl group from a donor peptide to an acceptor compound.

Question 37

What type of molecules can be acceptor of a gamma glutamyl group from a donor peptide?

Answer 37

Another peptide, an amino acid, or water

Question 38

Where is GGT found?

Answer 38

Found in most cells, in the cell membrane

Question 39

Where is the highest amounts of GGT found in the body?

Answer 39

In the kidney

Question 40

Besides, the kidney, where else can GGT be found?

Answer 40

Liver, prostate, pancreas and brain

Question 41

GGT found in the serum originates from what body system?

Answer 41

Hepatobiliary system

Question 42

What disease is GGT elevations sensitive for?

Answer 42

Liver disease

Question 43

Why is GGT the most sensitive out of all the liver enzymes?

Answer 43

It elevates first and persists longer

Question 44

GGT levels can help interpret elevated levels of what enzyme?

Answer 44

ALP

Question 45

If ALP and GGT are both elevated, what disease does this indicate?

Answer 45

Hepatic disease

Question 46

If ALP is elevated and GGT is normal, what does this say about the source of the ALP?

Answer 46

Nonhepatic source, like bone disease, pregnancy or childhood bone growth

Question 47

What drugs can induce GGT synthesis and elevate serum levels?

Answer 47

Alcohol intake, phenytoin and barbituates

Question 48

What specimen is preferred for GGT analysis?

Answer 48

Serum or EDTA plasma

Question 49

Why isn't heparin preferred for GGT analysis?

Answer 49

Heparin causes turbidity in the reaction mixture and thus, interferes with the measurement

Question 50

How long is the sample for GGT analysis stable at refrigerated temperature?

Answer 50

7 days

Question 51

How long is the sample used for GGT analysis stable if frozen?

Answer 51

2-3 months

Question 52

What is a common substrate used for GGT measurement?

Answer 52

Gamma-glutamyl-p-nitroanilide

Question 53

What is produced when GGT reacts with gamma-glutamyl-p-nitroanilide?

Answer 53

p-nitroaniline is formed

Question 54

What is measured in GGT analysis?

Answer 54

p-nitroaniline, which is yellow