Characteristics of hepatic alanine-glyoxylate aminotransferase in different mammalian species

Abstract

Mitochondrial extracts of dog, cat, rat and mouse liver contain two forms of alanine-glyoxylate aminotransferase (EC 2.6.1.44): one, designated isoenzyme 1, has mol.wt. approx. 80 000 and predominates in dog and cat liver; the other, designated isoenzyme 2, has mol.wt. approx. 175 000 and predominates in rat and mouse liver. In rat and mouse liver, isoenzyme 1 activity was increased by the injection in vivo of glucagon, but not isoenzyme 2 activity. Isoenzyme 1 was purified and characterized from liver mitochondrial extracts of the four species. Both rat and mouse enzyme preparations catalysed transamination between a number of L-amino acids and glyoxylate, and with L-alanine as amino donor the effective amino acceptors were glyoxylate, phenylpyruvate and hydroxypyruvate. In contrast, both dog and cat enzyme preparations were specific for L-alanine and L-serine with glyoxylate, and used glyoxylate and hydroxypyruvate as effective amino acceptors with L-alanine. Evidence that isoenzyme 1 is identical with serine-pyruvate aminotransferase (EC 2.6.1.51) was obtained. Isoenzyme 2 was partially purified from mitochondrial extracts of rat and mouse liver. Both enzyme preparations were specific for L-alanine and glyoxylate. On the basis of physical properties and substrate specificity, it was concluded that isoenzyme 2 is a separate enzyme. Some other properties of isoenzymes 1 and 2 are described.

Human Alanine-Glyoxylate Aminotransferase 2 Lowers Asymmetric Dimethylarginine and Protects from Inhibition of Nitric Oxide Production

“…Changes in the concentration of NADH, which is consumed during the conversion of pyruvate to lactate by LDH, were assessed by measuring absorbance at 340 nm. Under these reaction conditions, Tris forms an adduct with glyoxylate, preventing the use of glyoxylate as a substrate by LDH (28,29).…”

Alanine–glyoxylate aminotransferase-deficient mice, a model for primary hyperoxaluria that responds to adenoviral gene transfer

“…Mice were bred and maintained in a pathogen-free facility, with free access to standard chow (0.8% calcium͞0.5% PO 4 ; Letica, Barcelona, Spain) and water. Mice were placed in metabolic cages for a single mouse (Tecniplast, Exton, PA) and allowed to get acclimatized to a 5 g͞day powdered diet and distilled water for 3 days before the start of urine collection.…”

Novel Archaeal Alanine:Glyoxylate Aminotransferase from Thermococcus litoralis

“…The subunit structure of bacterial AGT has not yet been reported. In eucaryotes, peroxisomal AGTs are usually homodimers, with a subunit size of 38 to 45 kDa, whereas mitochondrial AGTs have a homotetrameric structure, with a subunit size of 50 to 56 kDa (16,23). H. methylovorum SGT, which shows 27% amino acid identity to human peroxisomal AGT, has been reported to have a homotetrameric structure with a subunit size of 40 kDa (10).…”

“…The enzyme is widely distributed in eucarya (16,26,33). One of the functions of AGT is the detoxification of glyoxylate.…”

“…Reverse transamination of the enzyme with 20 mM glycine and 5 mM pyruvate was examined by measuring the formation of L-alanine from pyruvate by use of an amino acid analyzer. A negative result was obtained; the enzyme was found to catalyze an irreversible transamination between L-alanine and glyoxylate, similar to AGTs from other sources (16,33). For screening of the AGT gene, an oligonucleotide mixture probe (a mixture of 128 sequences [5Ј-ATGGAYTAYACNA ARTAYYT-3Ј]) was synthesized based on the N-terminal amino acid sequence (underlined) of the enzyme as determined in this study (MDYTKYLAGRANWIKG).…”