Mansfeld Johanna, Ulbrich-Hofmann Renate
Martin-Luther University Halle-Wittenberg, Institute of Biochemistry and Biotechnology, Halle, Germany.
Biochim Biophys Acta. 2009 Sep;1791(9):913-26. doi: 10.1016/j.bbalip.2009.03.003. Epub 2009 Mar 12.
Most phospholipases D (PLDs) occurring in microorganisms, plants and animals belong to a superfamily which is characterized by several conserved regions of amino acid sequence including the two HKD motifs necessary for catalytic activity. Most eukaryotic PLDs possess additional regulatory structures such as the Phox and Pleckstrin homology domains in mammalian PLDs and the C2 domain in most plant PLDs. Owing to recombinant expression techniques, an increasing number of PLDs from different organisms has been obtained in purified form, allowing the investigation of specific and unspecific interactions of the enzymes with regulatory components in vitro. The present paper gives an overview on different factors which can modulate PLD activity and compares their influence on the enzymes from different sources. While no biological regulator can be recognized for extracellular bacterial PLDs, the most prominent specific activator of eukaryotic PLDs is phosphatidylinositol-4,5-bisphosphate (PIP(2)). In a sophisticated interplay PIP(2) seems to cooperate with several regulatory proteins in mammalian PLDs, whereas in plant PLDs it mainly acts in concert with Ca(2+) ions. Moreover, curvature, charges and heterogeneities of membrane surfaces are assessed as unspecific modulators. A possible physiological role of the transphosphatidylation reaction catalyzed by PLDs in competition with phospholipid hydrolysis is discussed.
大多数存在于微生物、植物和动物中的磷脂酶D（PLD）属于一个超家族，其特征是具有几个保守的氨基酸序列区域，包括催化活性所必需的两个HKD基序。大多数真核生物的PLD具有额外的调节结构，如哺乳动物PLD中的Phox和普列克底物蛋白同源结构域，以及大多数植物PLD中的C2结构域。由于重组表达技术，越来越多来自不同生物体的PLD已以纯化形式获得，这使得在体外研究这些酶与调节成分的特异性和非特异性相互作用成为可能。本文概述了可调节PLD活性的不同因素，并比较了它们对来自不同来源的酶的影响。虽然细胞外细菌PLD没有可识别的生物调节因子，但真核生物PLD最突出的特异性激活剂是磷脂酰肌醇-4,5-二磷酸（PIP(2)）。在一个复杂的相互作用中，PIP(2)似乎在哺乳动物PLD中与几种调节蛋白协同作用，而在植物PLD中，它主要与Ca(2+)离子协同作用。此外，膜表面的曲率、电荷和异质性被评估为非特异性调节剂。本文还讨论了PLD催化的转磷脂酰基反应在与磷脂水解竞争中的可能生理作用。
