title: Histidine 379 of human laeverin/aminopeptidase Q, a nonconserved residue within the exopeptidase motif, defines its distinctive enzymatic properties.
abstract: Human laeverin/aminopeptidase Q (LVRN/APQ) is a novel member of the M1 family of zinc aminopeptidases and is specifically expressed on the cell surface of human extravillous trophoblasts. Multiple sequence alignment of human M1 aminopeptidase revealed that the first Gly residue within the conserved exopeptidase motif of the M1 family, GXMEN motif, is uniquely substituted for His in human LVRN/APQ. In this study, we evaluated the roles of nonconserved His(379), comprising the exopeptidase motif in the enzymatic properties of human LVRN/APQ. We revealed that the substitution of His(379) with Gly caused significant changes in substrate specificity both toward fluorogenic substrates and natural peptide hormones. In addition, the susceptibilities of bestatin, a sensitive inhibitor for human LVRN/APQ, and natural inhibitory peptides were decreased in the H379G mutant. A molecular model suggested a conformational difference between wild-type and H379G human LVRN/APQs. These results indicate that His(379) of the enzyme plays essential roles in its distinctive enzymatic properties and contributes to maintaining the appropriate structure of the catalytic cavity of the enzyme. Our data may bring new insight into the biological significance of the unique exopeptidase motif of LVRN/APQ obtained during the evolution of primates.
authors.affiliation: Laboratory of Cellular Biochemistry, RIKEN, Wako, Saitama 351-0198.
authors.forename: Masato
authors.initials: M
authors.lastname: Maruyama
authors.forename: Naomi
authors.initials: N
authors.lastname: Arisaka
authors.forename: Yoshikuni
authors.initials: Y
authors.lastname: Goto
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Ohsawa
authors.forename: Hideshi
authors.initials: H
authors.lastname: Inoue
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujiwara
authors.forename: Akira
authors.initials: A
authors.lastname: Hattori
authors.forename: Masafumi
authors.initials: M
authors.lastname: Tsujimoto
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D004791:Enzyme Inhibitors / Q000378:metabolism; D019143:Evolution, Molecular; D020689:Exopeptidases / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D006639:Histidine / Q000378:metabolism*; D006801:Humans; D045726:Metalloproteases / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D011247:Pregnancy; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D010455:Peptides; D006639:Histidine; D020689:Exopeptidases; C482089:LVRN protein, human; D045726:Metalloproteases