Distinct enzymatic and cellular characteristics of two secretory phospholipases A2 in the filamentous fungus Aspergillus oryzae
Distinct enzymatic and cellular characteristics of two secretory phospholipases A2 in the filamentous fungus Aspergillus oryzae
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DOI：
10.1016/j.fgb.2009.12.011
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发表时间：
2010-04-01
影响因子：
3
通讯作者：
Arioka, Manabu
中科院分区：
文献类型：
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作者：
Nakahama, Tomoyuki;Nakanishi, Yoshito;Arioka, Manabu
微生物分泌型磷脂酶A（2）（sPLA（2）s）是这个功能多样的酶家族中最后发现的和最不为人所知的成员之一。本文分析了丝状子囊菌Aspergillus novel的两种sPLA（2），分别命名为sPlaA和sPlaB。sPlaA和sPlaB分别由222和160个氨基酸组成，并且共享微生物sPLA（2）s典型的保守Cys和催化His-Asp残基。两种sPLA（2）在最适pH、Ca 2+需求和表达谱方面不同。在碳饥饿，氧化应激和分生孢子过程中的splaA的mRNA强烈上调，而splaB的组成型表达在低水平和弱上调热休克。用sPLA（2）过表达菌株进行的实验表明，两种酶产生细微不同的磷脂组成变化，并且它们的亚细胞定位也不同：sPlaA在菌丝尖端最丰富并分泌到培养基中，而sPlaB主要定位于ER样细胞内区室。两种sPLA（2）过表达菌株的分生孢子都有缺陷，sPlaB过表达菌株的缺陷更为明显。虽然没有重大的形态异常检测到无论是三角洲splaA或三角洲splaB突变体，三角洲splaB的菌丝生长，但不是三角洲splaA，显示增加的敏感性H2 O2处理。这些数据表明，两个A.α-sPLA（2）酶显示出独特的、可能是非冗余的生理功能。(C)2009 Elsevier Inc. All rights reserved.
Microbial secretary phospholipases A(2) (sPLA(2)s) are among the last discovered and least known members of this functionally diverse family of enzymes. We analyzed here two sPLA(2)s, named sPlaA and sPlaB, of the filamentous ascomycete Aspergillus oryzae. sPlaA and sPlaB consist of 222 and 160 amino acids, respectively, and share the conserved Cys and catalytic His-Asp residues typical of microbial sPLA(2)s. Two sPLA(2)s differ in pH optimum, Ca2+ requirement and expression profile. The splaA mRNA was strongly upregulated in response to carbon starvation, oxidative stress and during conidiation, while splaB was constitutively expressed at low levels and was weakly upregulated by heat shock. Experiments with sPLA(2) overexpressing strains demonstrated that two enzymes produce subtly different phospholipid composition variations and also differ in their subcellular localization: sPlaA is most abundant in hyphal tips and secreted to the medium, whereas sPlaB predominantly localizes to the ER-like intracellular compartment. Both sPLA(2) overexpressing strains were defective in conidiation, which was more pronounced for sPlaB overexpressors. Although no major morphological abnormality was detected in either Delta splaA or Delta splaB mutants, hyphal growth of Delta splaB, but not that of Delta splaA, displayed increased sensitivity to H2O2 treatment. These data indicate that two A. oryzae sPLA(2) enzymes display distinct, presumably non-redundant, physiological functions. (C) 2009 Elsevier Inc. All rights reserved.