The regulation of glutamate metabolism in Candida utilis. Evidence for two interconvertible forms of NAD-dependent glutamate dehydrogenase.

An earlier observation from this laboratory (J. Gen. Microbiol. 64, 423--427) that NAD-dependent glutamate dehydrogenase activity is modulated by rapid inactivation has been extended to show that this mechanism is completely reversible. Changes in properties of the enzyme accompany inactivation and two different forms active (a) and inactive (b) of the enzyme with distinctive properties have been isolated. Incubation of the inactive enzyme with magnesium in vitro produced a rapid increase of activity; this was accompanied by a change in the properties of the enzyme to those of the a form. This control mechanism of enzyme interconversion appears widespread among yeasts. Its probable role in modulating glutamate synthesis and degration is discussed.