RELATIONSHIPS AMONGST SOME BACTERIAL AND YEAST LACTATE AND MANDELATE DEHYDROGENASES

Five yeast strains were isolated by enrichment culture on the basis of their ability to grow on mandelate and two of these strains were iden tified as Rhodotorula glutinis. In addition, a range of yeasts from cu lture collections was screened for growth on mandelate. The results su ggest that mandelate utilization is a widespread but not universal cha racteristic within the genus Rhodotorula. Several of the yeasts contai ned an inducible NAD-dependent D(-)-mandelate dehydrogenase and an ind ucible dye-linked (presumably flavoprotein) L(+)-mandelate dehydrogena se. All the D(-)-mandelate dehydrogenases from the yeasts showed immun ological cross-reactivity with each other (as judged by both immunoinh ibition and immunoblotting), as did all the yeast L(+)-mandelate dehyd rogenases that were tested. Determination of N-terminal amino acid seq uences of several bacterial and yeast lactate and mandelate dehydrogen ases, together with the evidence from the immunological studies, confi rmed and extended previous proposals that there are several major grou ps of such dehydrogenases: FMN-dependent, membrane-bound L(+)-lactate and L(+)-mandelate dehydrogenases (M(r) = approx. 44000) in bacteria, mitochondrial flavocytochrome b, L(+)-lactate and L(+)-mandelate dehyd rogenases (M(r) = approx. 59000) in yeasts, FAD-dependent. membrane-bo und D(-)-lactate and D(-)-mandelate dehydrogenases in bacteria, and so luble NAD-dependent D(-)-mandelate dehydrogenases in both bacteria and yeasts.