Gamma-Glutamyl Transferase

Gamma-Glutamyl Transferase

EC 2.3.2.2; y-glutamyl-peptide: amino acid y-glutamyltransferase; GGT

GGT catalyzes the transfer of the ___________ from _____________ and _______________ containing compounds.

y-glutamyl group

peptides and other y-glutamyl

The _______________ is the substrate itself, some ________________, in which case simple hydrolysis takes place.

y-glutamyl acceptor

amino acid or peptide, or even water

The enzyme acts only on ________________ containing a ______________ residue joined to the remainder of the compound through the ______________.

peptides or peptide-like compounds

terminal glutamate

terminal (-y-) carboxyl

Gamma-glutamyl transferase is primarily involved in ___________________, __________________, _________________.

peptide and protein synthesis, regulation of tissue glutathione levels and transport of amino acids across cell membranes

More so, it plays a major role in maintaining ___________________ which serves as an antioxidant for most free radicals, hence preventing possible occurrence of premature red cell destruction.

adequate intracellular levels of reduced glutathione

GGT is present (in _____________) in proximal renal tubule, liver, pancreas, and intestine.

decreasing order of abundance

The enzyme is present in ______________, but the larger fraction is located in the ______________ and may transport _______________ and _______________ into the cell across the cell membrane in the form of _______________.

cytoplasm (microsomes)

cell membrane

amino acids and peptides

y-glutamyl peptides

Though the kidneys have the higher GGT activity, GGT activity in serum comes primarily from the ____________.

liver

The enzyme present in serum appears to originate primarily from the ________________.

hepatobiliary system

GGT is a sensitive indicator of ___________being elevated in most patients with liver disease regardless of cause.

hepatobiliary disease,

Like ALP, it is highest in cases of ______________ (since it is located in the canaliculi of the liver), reaching activities some ________________.

intrahepatic or post-hepatic biliary obstruction

5 to 30 times upper reference limit

Within the hepatic parenchyma, GGT exists to a large extent in the ____________ and is, therefore, subject to ___________.

smooth endoplasmic reticulum

hepatic microsomal induction

GGT levels will be increased _____________ in patients receiving enzyme inducing drugs such as warfarin, phenobarbital, and phenytoin.

four times the normal upper limit

GGT is the most sensitive marker of ______________.

acute alcoholic hepatitis

Elevated activities of GGT are found in the sera of patients with _____________ and in the majority of sera of ______________.

alcoholic hepatitis

heavy drinkers

GGT assays are useful in monitoring the effects of _____________.

abstention from alcohol

Levels usually return to normal within __________ after cessation but can rise again if alcohol consumption is resumed.

two to three weeks

GGT levels are also elevated in other conditions, such as ____________, ________________, _____________.

acute pancreatitis, diabetes mellitus, and myocardial infarction

In AMI, GGT activity is usually normal. If there is a rise, it occurs at about the _______, reaches a maximum value in _________, and probably implies _____________.

fourth day

another 4 days

liver damage secondary to cardiac insufficiency

GGT activity is useful in differentiating the source of an elevated ALP level because GGT levels are normal in ______________ and _____________.

skeletal disorders and during pregnancy

It is particularly useful in evaluating ___________ in adolescents because ALP activity will invariably be elevated as a result of bone growth.

hepatobiliary involvement

GGT in urine is elevated in cases of ____________.

severe kidney disease

Values are also expected to be lower among__________ because of suppression of the activity resulting from _____________

females

estrogenic or progesterone hormones

Infants have __________ than adults because of the increase activity of hepatocyte but these levels decline to normal by about ______________.

higher GGT activity

six months after birth

In adults, the upper reference limit for GGT activity in serum is ____________ for females and ____________ for males.

38UIL for females and 55 UIL for males