Alanine aminotransferase and glycine aminotransferase from maize (Zea mays L.) leaves.
Alanine aminotransferase (AlaAT, EC 2.6.1.2) and glycine aminotransferase (GlyAT, EC 2.6.1.4), two different enzymes catalyzing transamination reactions with L-alanine as the amino-acid substrate, were examined in maize in which alanine participates substantially in nitrogen transport. Preparative PAGE of a partially purified preparation of aminotransferases from maize leaves gave 6 fractions differing in electrophoretic mobility. The fastest migrating fraction I represents AlaAT specific for L-alanine as amino donor and 2-oxoglutarate as amino acceptor. The remaining fractions showed three aminotransferase activities: L-alanine-2-oxoglutarate, L-alanine-glyoxylate and L-glutamate-glyoxylate. By means of molecular sieving on Zorbax SE-250 two groups of enzymes were distinguished in the PAGE fractions: of about 100 kDa and 50 kDa. Molecular mass of 104 kDa was ascribed to AlaAT in fraction I, while the molecular mass of the three enzymatic activities in 3 fractions of the low electrophoretic mobility was about 50 kDa. The response of these fractions to: aminooxyacetate, 3-chloro-L-alanine and competing amino acids prompted us to suggest that five out of the six preparative PAGE fractions represented GlyAT isoforms, differing from each other by the L-glutamate-glyoxylate:L-alanine-glyoxylate:L-alanine-2-oxoglutarate activity ratio.
Orzechowski
S
S
Department of Biochemistry, Faculty of Agriculture, Warsaw Agricultural University, Warszawa, Poland.
Socha-Hanc
J
J
Paszkowski
A
A
D000410:Alanine Transaminase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D051308:Glycine Transaminase; D008970:Molecular Weight; D018515:Plant Leaves / Q000201:enzymology; D000637:Transaminases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D003313:Zea mays / Q000201:enzymology*
D000637:Transaminases; D000410:Alanine Transaminase; D051308:Glycine Transaminase