Induction of l-Serine Dehydratase in Aeromonas punctata

l -Serine dehydratase (SD) was produced to the extent of only 0·04 international unit (iu) per mg dry weight by Aeromonos punctata NRRL B-928 when grown on a chemically defined medium. Addition of 2% (w/v) l -serine to this medium increased SD ten-fold or more, indicating a significant inductive effect. d -Serine was toxic to the organism, making weights and enzyme titres uncertain, but dl -serine induced a specific activity of SD at least equal to that from the l enantiomorph. With complex media containing beef extract, the toxic effect of d -serine was partially overcome, and sufficient growth was obtained to permit reliable analytical figures; d -serine induced slightly better specific activities than the l isomer. dl -Serine at 2% concentration induced a specific activity of 1·2 iu/mg, twice that of l -serine at that level.