Phospholipase A2. Methods for Activity Monitoring
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Phospholipase A2. Methods for Activity Monitoring A. S. Alekseevaa and I. A. Boldyreva, * a
Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997 Russia *e-mail: [email protected] Received May 7, 2020; revised May 13, 2020; accepted May 14, 2020
Abstract—Phospholipases A2 (PLA2) are hydrolytic proteins, which cleave fatty acid off the second position (sn-2) of the phospholipid. An increased activity of PLA2 correlates with the course of many different inflammatory processes in the body. For the purpose of diagnosing and predicting pathological processes, systems for detecting the PLA2 activity are being developed. The key component of all test systems is a substrate of lipid or non-lipid nature, the breakdown of which by the enzyme leads to the appearance of analytical signal. Lipids as such do not absorb light in the visible region and do not fluoresce. Therefore, to determine the activity of PLA2, substrates with various labels are developed. Test systems for determination of the PLA2 activity can be divided into three groups, depending on the stage of the enzyme action a signal is formed at: (1) systems based on the detection of hydrolysis products; (2) systems based on the cleavage of fluorescently labeled substrates, and (3) systems based on the detection of membrane disintegration. Each of these groups has its own requirements for the structure of the substrate. This review is focused on the structure of PLA2 substrates used in systems to determine the enzyme activity; the proposed classification allows one to identify the strengths and weaknesses of existing detection systems and will be relevant when designing new test systems. Keywords: phospholipase A2, enzyme activity, lipids, PLA2 substrates, fluorescent probes DOI: 10.1134/S1990747820040030
INTRODUCTION Phospholipases A2 (PLA2) is a large superfamily of proteins with a hydrolytic activity against phospholipids, which can selectively cleave fatty acid at the second position (sn-2) of phospholipid. As of today, six PLA2 families are typically distinguished: secreted, cytosolic, Ca2+-independent, platelet-activating factor acetylhydrolases (including lipoprotein-associated PLA2), lysosomal PLA2s, and PLA2 in adipose tissue. The family of secreted PLA2s is the most numerous and includes ten groups comprising several subgroups. Secreted (extracellular) PLA2s are found in all mammalian tissues and contained in the venom of snakes and insects. Due to their catalytic activity, PLA2 can release fatty acids (e.g., arachidonic acid) for cyclooxigenases, lipoxygenases, and cytochrome P450 enzymes, which in turn produce different inflammatory mediators including leukotrienes, thromboxanes, and prostaglandins. The most comprehensive description of structural peculiarities, mechanisms of action, localization, and importance for organisms of each type of PLA2 can be found in the reviews [1, 2]. Endogenous PLA2 is of interest for researchers due to the broad range of pathologies involving this enzyme (see reviews [
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