Cyanide metabolism in higher plants: III. The biosynthesis of β-cyanolanine

Blumenthal, S. G. ; Hendrickson, H. R. ; Abrol, Y. P. ; Conn , Eric E. (1968) Cyanide metabolism in higher plants: III. The biosynthesis of β-cyanolanine The Journal of Biological Chemistry, 243 . pp. 5302-5307. ISSN 0021-9258

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Seedlings of blue lupine, sorghum, and common vetch which convert H14CN extensively into the amide carbon of asparagine have been shown to utilize L-cysteine-3-14C as the source of the other 3 carbon atoms of asparagine. The presence of HCN in the atmosphere in which the plants are grown greatly stimulates the conversion of 14C in the cysteine into asparagine. L-Serine-1-14C is also converted into asparagine by sorghum seedlings, and the amount of conversion is stimulated 3-fold by HCN. Seedlings of common vetch also convert L-serine-1-14C into the β -cyanoalanine moiety of the lathyritic dipeptide γ-glutamyl-β -cyanoalanine, but this conversion is not affected by the presence of HCN. Buffered extracts of acetone powders of seedlings of sorghum, blue lupine, common vetch, and bird's-foot trefoil catalyze the formation of β -cyanoalanine and H2S from l-cysteine and HCN. The enzyme responsible, which has been tentatively named β -cyanoalanine synthase, may be exhibited by incubating radioactive L-cysteine or H14CN with the extracts and the other unlabeled substrate and measuring the β -cyanoalanine-14C formed. The enzyme may also be assayed by measuring colorimetrically the H2S formed. H14C15N is converted by sorghum seedlings to the amide group of asparagine without any separation of the C and N atoms of the cyanide group.

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ID Code:28854
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