Increased phospholipase A activities in sera of intensive-care patients show sn-2 specificity but no acyl-chain selectivity.
Phospholipase A (PLA) activities were measured by high-performance liquid chromatography in two enzyme preparations purified from human duodenal juice and a serum pool as well as in 52 sera from 31 intensive-care patients with various diseases. On the basis of a position-specific fatty acid analysis of the natural substrate ("soybean lecithin") from a commercial PLA kit, serum activities of PLA1 could be clearly distinguished from those of PLA2, which is not possible in the usual measurements made with single-label radioactive substrates. Independent of the type of disease, all sera with highly increased PLA activities (40-200 U/L) showed nearly pure PLA2 characteristics without any preference among oleic, linoleic, and linolenic acid in the sn-2 position of the glycerophospholipid substrate. Nevertheless, very low PLA1 activities (< or = 5 U/L, most likely due to heparin perfusion therapy) could also be detected by palmitic and stearic acid release from the sn-1 position, leading to small changes in fatty acid release patterns of sera with low PLA activities. Measurements with sera from heparin-treated volunteers demonstrated that heparin therapy may initially contribute as much as 22 U/L to increased PLA1 activities but is not important under prolonged therapy. The absence of selectivity with respect to acyl-chain desaturation supports the concept of serum PLA2 as an acute-phase protein rather than a regulator of the arachidonic acid cascade.
Püttmann
M
M
Institut für Klinische Chemie, Klinikum Mannheim, Universität Heidelberg, Germany.
Aufenanger
J
J
von Ochsenstein
E
E
Dürholt
S
S
van Ackern
K
K
Harenberg
J
J
Hoffmann
G E
GE
D000328:Adult; D000368:Aged; D002851:Chromatography, High Pressure Liquid; D003422:Critical Care; D004386:Duodenum / Q000201:enzymology; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism*; D005260:Female; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D008297:Male; D008875:Middle Aged; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D010713:Phosphatidylcholines / Q000032:analysis / Q000378:metabolism; D010741:Phospholipases A / Q000032:analysis / Q000097:blood*; D054466:Phospholipases A1; D054467:Phospholipases A2; D010743:Phospholipids / Q000032:analysis / Q000378:metabolism; D012016:Reference Values; D013025:Glycine max; D013379:Substrate Specificity
D005227:Fatty Acids; D010169:Palmitic Acids; D010713:Phosphatidylcholines; D010743:Phospholipids; D019308:Palmitic Acid; D006493:Heparin; D010741:Phospholipases A; D054466:Phospholipases A1; D054467:Phospholipases A2