Studies of aromatic biosynthetic and catabolic enzymes inUstilago maydisand in mutants ofU. violacea

Abstract

SUMMARY: A multienzyme complex for five of the enzymes in the prechorismate portion of the aromatic biosynthetic pathway has been demonstrated inUstilago violacea, and has previously been reported inU. maydis(Ahmed & Giles, 1969). This complex is similar to that found inNeurospora crassaand other fungi. InU. violaceapolyaromatic-requiring mutants show pleiotropic deficiencies for all five of these enzymes, similar to the extreme pleiotropic polar mutants of thearomgene cluster in Neurospora (Giles, Case, Partridge & Ahmed, 1967a; Case & Giles, 1971). This result is interpreted as mutational evidence for anaromgene cluster inU. violaceacomparable to that inN. crassa. A second low molecular weight, heat-stable isozyme of dehydroquinase is shown to be present at high (constitutive) levels inU. maydis, as previously indicated by Ahmed & Giles (1969), but this activity is increased to extraordinarily high levels in cells grown in the presence of quinate. In contrast,U. violaceastrains do not grow on quinate, have a single, heat-labile dehydroquinase species, and lack activities for other enzymes in the quinate catabolic pathway.