A further series of mutant am alleles, encoding potentially active NADP-specific glutamate
dehydrogenase (GDH) and capable of complementation in heterocaryons, have been characterized
with respect to both GDH properties and DNA sequence changes. Several mutants previously
studied, and some of their same-site or second-site revertants, have also been sequenced for the
first time. We present a summary of what is known of the properties of all am mutants that have
been defined at the sequence level.