Sequence studies on D-serine dehydratase of Escherichia coli. Primary structure of the tryptic phosphopyridoxyl peptide and of the N-terminus.

An improved procedure for large-scale production of crystalline D-serine dehydratase (EC 4.2.1.14) from Escherichia coli is described. The N-terminal sequence of the enzyme (Mr 45500) was determined in a solid-phase sequencer as Met-Glu-Asn-Ala-Lys-Met-Asn-Ser-Leu-Ile-Ala-Gln-Tyr-Pro-Leu-Val-Lys-Asp-Leu-Val-Ala-LEU-Lys. Four of the first five N-terminal residues are homologeous with tryptophanase, another pyridoxal-phosphate (P-Pxy) enzyme that catalyzes alpha,beta-elimination reactions. After borohydride reduction and tryptic digestion of the enzyme, a peptide was isolated showing the sequence Lys-Asp-Ser-His-Leu-Pro-Ile-Ser-Gly-Ser-Ile-Lys(P-Pxy)-Ala-Arg. No clear homology of this portion of the enzyme with tryptophanase or another pyridoxal-phosphate enzyme was observed.