Biosynthesis of lysine in Rhodotorula glutinis: role of pipecolic acid

Abstract

Glutamate-alpha-ketoadipate transaminase, saccharopine reductase, and saccharopine dehydrogenase activities were demonstrated in extracts of Rhodotorula glutinis but alpha-aminoadipate reductase activity could not be measured in whole cells or in extracts. Lysine auxotroph lys1 grew in the presence of L-lysine or DL-alpha-aminoadipate and incorporated radioactivity from DL-alpha-amino-[I-14C]adipate into lysine during growth. Growing wild-type cells converted L-[U-14C]lysine into alpha-amino-[14C]adipate, suggesting both biosynthetic and degradative roles for alpha-aminoadipate. Lysine auxotrophs lys1, lys2 and lys3 of R. glutinis, unlike lysine auxotrophs of Saccharomyces cerevisiae, satisfied their growth requirement with L-pipecolate. Moreover, extracts of wild-type R. glutinis catalysed the conversion of L-pipecolate to alpha-aminoadipate-delta semialdehyde. These results suggest a biosynthetic role for L-pipecolate in R. glutinis but not in S. cerevisiae.