P-Cyanoalanine synthase

Plants convert HCN into asparagine (75) and p-cyano-alanine (76) (Fig. 16.15). When H CN is introduced in plants, the label is incorporated into the amide carbon of asparagine (Davis, 1991). This suggests that the cyanogenic compounds are being synthesized and catabolized, and the HCN produced in the intact plant is subsequently incorporated into asparagine by the action of 3-cyanoalanine synthase and (3-cyanoalanine hydrolase. (3-Cyanoalanine synthase has been shown to occur in many plants (Conn, 1981 Harbome, 1989 Nahrstedt, 1992). 

Scheme 45). When samples of (3S)- and (3R)-[3- Hi]cysteine 134, and 134, Hg = H, respectively, prepared using 0-acetylserine sulfhydrase as above, were incubated with this synthase and the resultant samples of )S-cyanoalanine 144 were degraded to malates 83a via aspartates, the pro-R specific enzyme fumarase could be used to assess the stereochemistry, as shown in Scheme 45 (87). The P replacement 134 144 again occurred with... 

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