CYSTEINE-S-CONJUGATE BETA-LYASE ACTIVITY AND PYRIDOXAL-PHOSPHATE BINDING-SITE OF ONION ALLIIN LYASE

Purification of onion alliin lyase gave two fractions by cation exchan ge chromatography. Both fractions showed the comparable high catalytic activity of cysteine-S-conjugate beta-lyase with that of alliin lyase using S-(2-chloro-6-nitrophenyl)-L-cysteine and alliin, S-allyl-L-cys teine sulfoxide as substrates. All the active substrates tested with o nion alliin lyase were also active to the cysteine-S-conjugate beta-ly ase of Mucor javanicus, but the catalytic activity of the Mucor enzyme was lower for all the substrates, The pyridoxal phosphate binding sit e of the onion alliin lyase was identified as Lys 285 in the amino aci d sequence deduced from cDNA which has been reported, This lysine was conserved in all the sequences from the alliin lyase cDNAs, while simi larity was not found between the sequences around pyridoxal phosphate binding sites of both the onion alliin lyase and the Mucor cysteine-S- conjugate beta-lyase.