Characteristics and sequence of phosphoglycolate phosphatase from a eukaryotic green alga Chlamydomonas reinhardtii.
Phosphoglycolate phosphatase (PGPase), a key enzyme of photorespiration in photosynthetic organisms, was purified from Chlamydomonas reinhardtii. The enzyme was an approximately 65-kDa homodimer with a pI value of 5.1 composed of approximately 32-kDa subunits not connected by any S-S bridges. It was also highly specific for phosphoglycolate with a K(m) value of 140 microm and an optimal pH between 8 and 9. The activity was strongly inhibited by CaCl(2), and it recovered competitively following the addition of MgCl(2) or EGTA. A mobility shift was observed in SDS-polyacrylamide gel electrophoresis by the addition of CaCl(2), indicating that the enzyme binds to Ca(2+). The N-terminal region of amino acid sequence deduced from cDNA sequence that was not contained in the purified PGPase had similar characteristics to those of typical stroma-targeting transit peptides in C. reinhardtii. The following region of the deduced sequence containing 302 amino acid residues was similar to p-nitrophenylphosphatase-like proteins, although the purified PGPase did not hydrolyze p-nitrophenylphosphate. Genomic DNA fragments from wild type containing the sequence homologous to the cDNA for PGPase complemented the PGPase-deficient mutant pgp1. Possible regulatory mechanisms during adaptation to limiting CO(2) were discussed based on the characteristics of the purified PGPase and the deduced amino acid sequence.
Mamedov
T G
TG
Plant Physiology Laboratory, Tohoku National Agricultural Research Center, Shimo-Kuriyagawa, Morioka 020-0198, Japan.
Suzuki
K
K
Miura
K
K
Kucho Ki
K
K
Fukuzawa
H
H
D000388:Air; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D016825:Chlamydomonas reinhardtii / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D012333:RNA, Messenger; C022408:phosphoglycolate phosphatase; D010744:Phosphoric Monoester Hydrolases