Human pyridoxal phosphatase. Molecular cloning, functional expression, and tissue distribution.
Pyridoxal phosphatase catalyzes the dephosphorylation of pyridoxal 5'-phosphate (PLP) and pyridoxine 5'-phosphate. A human brain cDNA clone was identified to the PLP phosphatase on the basis of peptide sequences obtained previously. The cDNA predicts a 296-amino acid protein with a calculated Mr of 31698. The open reading frame is encoded by two exons located on human chromosome 22q12.3, and the exon-intron junction contains the GT/AG consensus splice site. In addition, a full-length mouse PLP phosphatase cDNA of 1978 bp was also isolated. Mouse enzyme encodes a protein of 292 amino acids with Mr of 31512, and it is localized on chromosome 15.E1. Human and mouse PLP phosphatase share 93% identity in protein sequence. A BLAST search revealed the existence of putative proteins in organism ranging from bacteria to mammals. Catalytically active human PLP phosphatase was expressed in Escherichia coli, and characteristics of the recombinant enzyme were similar to those of erythrocyte enzyme. The recombinant enzyme displayed Km and kcat values for pyridoxal of 2.5 microM and 1.52 s(-1), respectively. Human PLP phosphatase mRNA is differentially expressed in a tissue-specific manner. A single mRNA transcript of 2.1 kb was detected in all human tissues examined and was highly abundant in the brain. Obtaining the molecular properties for the human PLP phosphatase may provide new direction for investigating metabolic pathway involving vitamin B6.
Jang
Young Min
YM
Department of Biochemistry, Kyungpook National University, Taegu 702-701, Korea.
Kim
Dae Won
DW
Kang
Tae-Cheon
TC
Won
Moo Ho
MH
Baek
Nam-In
NI
Moon
Byung Jo
BJ
Choi
Soo Young
SY
Kwon
Oh-Shin
OS
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D002884:Chromosomes, Human, Pair 15; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D019992:Databases as Topic; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D005091:Exons; D006801:Humans; D007438:Introns; D007700:Kinetics; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010455:Peptides / Q000737:chemistry; D010744:Phosphoric Monoester Hydrolases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D025101:Vitamin B 6 / Q000378:metabolism
D018076:DNA, Complementary; D010455:Peptides; D012333:RNA, Messenger; D011994:Recombinant Proteins; D025101:Vitamin B 6; C022493:pyridoxal-5-phosphatase; D010744:Phosphoric Monoester Hydrolases