title: Sepiapterin reductases from Chlorobium tepidum and Chlorobium limicola catalyze the synthesis of L-threo-tetrahydrobiopterin from 6-pyruvoyltetrahydropterin.
abstract: The ORF sequences of the gene encoding sepiapterin reductase were cloned from the genomic DNAs of Chlorobium tepidum and Chlorobium limicola, which are known to produce L-threo- and L-erythro-tetrahydrobiopterin (BH4)-N-acetylglucosamine, respectively. The deduced amino acid sequence of C. limicola consists of 241 residues, while C. tepidum SR has three residues more at the C-terminal. The overall protein sequence identity was 87.7%. Both recombinant proteins generated from Escherichia coli were identified to catalyze reduction of diketo compound 6-pyruvoyltetrahydropterin to L-threo-BH4. This result suggests that C. limicola needs an additional enzyme for L-erythro-BH4 synthesis to yield its glycoside. The catalytic activity of Chlorobium SRs also supports the previously proposed mechanism of two consecutive reductions of C1' carbonyl group of 6-pyruvoyltetrahydropterin via isomerization reaction.
authors.affiliation: School of Biotechnology and Biomedical Science, Inje University, Kimhae 621-749, Republic of Korea.
authors.forename: Yong Kee
authors.initials: YK
authors.lastname: Choi
authors.forename: Si-Reong
authors.initials: SR
authors.lastname: Jun
authors.forename: Eun-Young
authors.initials: EY
authors.lastname: Cha
authors.forename: Jung Soon
authors.initials: JS
authors.lastname: Park
authors.forename: Young Shik
authors.initials: YS
authors.lastname: Park
mesh_terms: D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D001708:Biopterins / Q000031:analogs & derivatives* / Q000096:biosynthesis*; D041883:Chlorobium / Q000201:enzymology* / Q000235:genetics; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011622:Pterins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D011622:Pterins; D011994:Recombinant Proteins; D001708:Biopterins; C045652:dyspropterin; D000429:Alcohol Oxidoreductases; C022630:sepiapterin reductase; C003402:sapropterin