As. Srivastava et al., Activity and expression of aspartate aminotransferase during the reproductive cycle of a fresh water fish, Clarias batrachus, FISH PHYS B, 20(3), 1999, pp. 243-250
Aspartate amino transferase (AspT; EC: 2.6.1.1) is one of the key enzyme of
aspartate malate shuttle and non-essential amino acid metabolism. In order
to clarify the change of the activities of both cytosolic (c-) and mitocho
ndrial (m-) AspT isoenzymes during the different reproductive stages of Cla
rias batrachus, an air-breathing carnivorous freshwater fish, the c- and m-
AspT activities were measured spectrophotometrically in liver, heart, kidn
ey, brain and ovary during the pre-spawning, spawning and post-spawning pha
ses of the annual reproductive cycle of this fish. Maximum activities were
observed during the spawning phase, followed by pre- and postspawning phase
s. The native agarose gel electrophoretic pattern revealed two AspT forms,
c-AspT and m-AspT, throughout the pre- to post-spawning phases. However, th
e spawning phase was marked by the expression of an additional anionic form
of c-AspT in all tissues studied. These results indicate a distinct utiliz
ation of aspartate particularly in the spawning phase in fish in the centra
l metabolic path via transamination reactions, and suggest a control of the
enzyme activity by the expression of the additional c-AspT gene, especiall
y at the spawning phase.