S-ADENOSYL-L-HOMOCYSTEINE HYDROLASE FROM XENOPUS-LAEVIS - IDENTIFICATION, DEVELOPMENTAL EXPRESSION AND EVOLUTION

S-Adenosyl-L-homocysteine hydrolase (EC 3.3.1.1) is an important enzym e in the trans-sulphuration pathway, mediating the conversion of S-ade nosyl-L-homocysteine to adenosine and L-homocysteine. We have identifi ed a cDNA clone from Xenopus laevis, encoding a protein of 433 aa, whi ch is highly conserved with S-Adenosyl-L-homocysteine hydrolases (Adoh cyases) from other species. Expression of Adohcyase mRNA in X.laevis t adpoles is detectable from developmental Stage 27 onwards. Phylogeneti c analysis of available Adohcyase sequences indicates that species clu ster essentially as predicted from morphological data. Furthermore, we estimate that S-adenosyl-L-homocysteine hydrolase is evolving very sl owly, almost 10 times slower than the average rate. (C) 1994 Academic Press, Inc.