Histidine 379 of Human Laeverin/Aminopeptidase Q, a Nonconserved Residue within the Exopeptidase Motif, Defines Its Distinctive Enzymatic Properties
Histidine 379 of Human Laeverin/Aminopeptidase Q, a Nonconserved Residue within the Exopeptidase Motif, Defines Its Distinctive Enzymatic Properties
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DOI：
10.1074/jbc.m109.066712
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发表时间：
2009-12-11
影响因子：
4.8
通讯作者：
Tsujimoto, Masafumi
中科院分区：
文献类型：
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作者：
Maruyama, Masato;Arisaka, Naomi;Tsujimoto, Masafumi
人左旋氨肽酶Q（LVRN/APQ）是锌氨肽酶M1家族的新成员，特异性表达于人绒毛外滋养层细胞表面。人M1氨肽酶的多重序列比对显示，M1家族保守的外肽酶基序GXMEN基序内的第一个Gly残基在人LVRN/APQ中唯一地取代His。在这项研究中，我们评估了非保守的His（379），包括人LVRN/APQ的酶性质的外肽酶基序的作用。我们发现，用Gly取代His（379）会导致荧光底物和天然肽激素的底物特异性发生显着变化。此外，在H379 G突变体中，人LVRN/APQ的敏感抑制剂bestatin和天然抑制肽的亲和力降低。分子模型表明野生型和H379 G人LVRN/APQ之间的构象差异。这些结果表明，His（379）在其独特的酶促性质中起着至关重要的作用，并有助于维持酶的催化腔的适当结构。我们的数据可能会带来新的见解独特的外肽酶基序的生物学意义的LVRN/APQ在灵长类动物的进化过程中获得。
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.