Generation of aspartate aminotransferase multiple forms by deamidation.

The development of aspartate aminotransferase subforms in vitro was followed by densitometry after thin-film isoelectric focusing. At the same time ammonia production was measured. Each reaction can be expressed in terms of a first-order process in which 2 mol of glutamine or asparagine/mol of dimer are deamidated with a half time of 22 days. The more negatively charged subforms developed in vitro were almost fully active. Another process occurred leading to inactivation by coenzyme modification, and this was independent of deamidation. Although the enzyme formed absorbed maximally at 340nm, it was different from the naturally occurring inactive enzyme that absorbs at this wavelength.