L-RHAMNOSE METABOLISM IN PICHIA-STIPITIS AND DEBARYOMYCES-POLYMORPHUS

The pathway for the breakdown of L-rhamnose by the yeast Pichia stipit is NRC 5568 was shown to involve nonphosphorylated intermediates and t o produce pyruvate and L-lactaldehyde. The activities of the enzymes a nd the nature of several intermediates were determined. The enzymes in volved are L-rhamnose dehydrogenase, L-rhamnonate dehydratase, and 2-k eto-3-deoxy-L-rhamnonate aldolase. This pathway was found to be induci ble by L-rhamnose and repressed by D-glucose. These enzymes were also present in a mutant of P. stipitis (PR1) resistant to catabolite repre ssion and in Debaryomyces polymorphus 1747. Cell-free extracts of P. s tipitis and D. polymorphus grown in L-rhamnose as sole carbon source w ere found to contain NAD(+)-dependent aldehyde dehydrogenase activitie s.