Chlorophyllase as a serine hydrolase: identification of a putative catalytic triad.
Chlorophyllases (Chlases), cloned so far, contain a lipase motif with the active serine residue of the catalytic triad of triglyceride lipases. Inhibitors specific for the catalytic serine residue in serine hydrolases, which include lipases effectively inhibited the activity of the recombinant Chenopodium album Chlase (CaCLH). From this evidence we assumed that the catalytic mechanism of hydrolysis by Chlase might be similar to those of serine hydrolases that have a catalytic triad composed of serine, histidine and aspartic acid in their active site. Thus, we introduced mutations into the putative catalytic residue (Ser162) and conserved amino acid residues (histidine, aspartic acid and cysteine) to generate recombinant CaCLH mutants. The three amino acid residues (Ser162, Asp191 and His262) essential for Chlase activity were identified. These results indicate that Chlase is a serine hydrolase and, by analogy with a plausible catalytic mechanism of serine hydrolases, we proposed a mechanism for hydrolysis catalyzed by Chlase.
Tsuchiya
Tohru
T
Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama, Kanagawa, 226-8501 Japan. ttsuchiy@bio.titech.ac.jp
Suzuki
Takuo
T
Yamada
Takafumi
T
Shimada
Hiroshi
H
Masuda
Tatsuru
T
Ohta
Hiroyuki
H
Takamiya
Ken-ichiro
K
D000595:Amino Acid Sequence; D001224:Aspartic Acid / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D027463:Chenopodium album / Q000201:enzymology / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006639:Histidine / Q000235:genetics; D006868:Hydrolysis; D007531:Isoflurophate / Q000494:pharmacology; D008049:Lipase / Q000378:metabolism; D008969:Molecular Sequence Data; D009025:Morpholines / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000235:genetics; D012697:Serine Endopeptidases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020245:p-Chloromercuribenzoic Acid / Q000494:pharmacology
D004791:Enzyme Inhibitors; D009025:Morpholines; D007531:Isoflurophate; C008550:morpholinopropane sulfonic acid; D001224:Aspartic Acid; D012694:Serine; D006639:Histidine; D010664:Phenylmethylsulfonyl Fluoride; D020245:p-Chloromercuribenzoic Acid; D002265:Carboxylic Ester Hydrolases; C019875:chlorophyllase; D008049:Lipase; D012697:Serine Endopeptidases