Tryptophanase-catalyzed L-tryptophan synthesis from D-serine in the presence of diammonium hydrogen phosphate.
Tryptophanase, an enzyme with extreme absolute stereospecificity for optically active stereoisomers, catalyzes the synthesis of l-tryptophan from l-serine and indole through a beta-substitution mechanism of the ping-pong type, and has no activity on d-serine. We previously reported that tryptophanase changed its stereospecificity to degrade d-tryptophan in highly concentrated diammonium hydrogen phosphate, (NH(4))(2)HPO(4) solution. The present study provided the same stereospecific change seen in the d-tryptophan degradation reaction also occurs in tryptophan synthesis from d-serine. Tryptophanase became active to d-serine to synthesize l-tryptophan in the presence of diammonium hydrogen phosphate. This reaction has never been reported before. d-serine seems to undergo beta-replacement via an enzyme-bonded alpha-aminoacylate intermediate to yield l-tryptophan.
Shimada
Akihiko
A
Sustainable Environmental Studies, Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan.
Ozaki
Haruka
H
Sustainable Environmental Studies, Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan.
Saito
Takeshi
T
Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan.
Noriko
Fujii
F
Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan.
D055162:Biocatalysis; D002855:Chromatography, Thin Layer; D002942:Circular Dichroism; D010710:Phosphates / Q000737:chemistry*; D012492:Salts / Q000737:chemistry; D012694:Serine / Q000737:chemistry / Q000378:metabolism*; D013237:Stereoisomerism; D014364:Tryptophan / Q000096:biosynthesis*; D014368:Tryptophanase / Q000378:metabolism*
D010710:Phosphates; D012492:Salts; C024788:ammonium phosphate; D012694:Serine; D014364:Tryptophan; D014368:Tryptophanase