title: Modulating the function of human serine racemase and human serine dehydratase by protein engineering.
abstract: D-Serine is a co-agonist of N-methyl D-aspartate, a glutamate receptor, which is a major excitatory neurotransmitter receptor in the brain. Human serine racemase (hSR) and serine dehydratase (hSDH) are two important pyridoxal-5'-phosphate-dependent enzymes that synthesize and degrade D-serine, respectively. hSR and hSDH have significant sequence homology (28% identity) and are similar in their structural folds (root-mean-square deviation, 1.12 Å). Sequence alignment and structural comparison between hSR and hSDH reveal that S84 in hSR and A65 in hSDH play important roles in their respective enzyme activities. We surmise that exchange of these two amino acids by introducing S84A hSR and A65S hSDH mutants may result in switching their protein functions. To understand the modulating mechanism of the key residues, mutants S84A in hSR and A65S in hSDH were constructed to monitor the change of activities. The structure of A65S hSDH mutant was determined at 1.3 Å resolution (PDB 4H27), elucidating the role of this critical amino acid. Our study demonstrated S84A hSR mutant behaved like hSDH, whereas A65S hSDH mutant acquired an additional function of using D-serine as a substrate.
authors.affiliation: Institute of Biological Chemistry,  Academia Sinica, Taipei 11529,  Taiwan.
authors.forename: Cyong-Yi
authors.initials: CY
authors.lastname: Wang
authors.forename: Shan Chi
authors.initials: SC
authors.lastname: Ku
authors.forename: Cheng-Chung
authors.initials: CC
authors.lastname: Lee
authors.forename: Andrew H-J
authors.initials: AH
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D006801:Humans; D012695:L-Serine Dehydratase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D015202:Protein Engineering; D019998:Racemases and Epimerases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D017385:Sequence Homology; D000099300:Serine Racemase
chemical_list: D012695:L-Serine Dehydratase; D019998:Racemases and Epimerases; D000099300:Serine Racemase