[Relationship between postmortem change and biological reaction].

Abstract

In the adipocere which is one of postmortem changes, some specific fatty acids possessing higher melting points together with soap play an important role in the formation of adipocere. These fatty acids were clarified to be mainly 10-hydroxystearic and 10-hydroxypalmitic acids. Moreover, slight amounts of 10-oxostearic and 10-oxopalmitic acids, which have higher melting points than those of hydroxy fatty acids, exist in the adipocere as well. The substantial adipocere is formed and stabilized by these specific fatty acids together with the soap. The hydroxy fatty acid (OHFA) and oxo fatty acid (OXOFA) are biosynthesized by some enzymes from bacteria. Various aerobic and anaerobic bacteria are involved in the formation of adipocere. For example, microbial conversion of various unsaturated fatty acids to 10-OHFA by Micrococcus luteus was investigated. As a result, 10-OHFA was synthesized only from fatty acids possessing cis-9-unsaturation. It was also clarified that 10-OHFAs were converted to the corresponding 10-OXOFAs but the 10-OXO compounds were inactive as substrates. Furthermore, the enzyme preparations from Flavobacterium meningosepticum solubilized by sonication catalyzed not only hydration of oleic acid to produce 10-hydroxystearic acid but also dehydrogenation of this product in the presence of deuterium. On the other hand, we found out that there was 10-hydroxy-12-octadecenoic acid (10-OHLA) from linoleic acid in some kinds of adipocere. 10-OHFA existing in adipocere has been thought not to exist in a living body. However, recently 10-epoxy-12-octadecenoic acid (leukotoxin, LTx) which is one of lipid peroxides was found not only in rice plants but in polymorphonuclear leukocytes. It was also clarified that these polymorphonuclear leukocytes produced the same 10-OHLA as the compound found in adipocere. Since LTx was found from leukocytes related to inflammatory response, it has been interested in involvement of not only the basic mechanism of biological defense but also the mechanism of shock as a vasoactive substance. A postmortem change itself is little associated with a phenomenon on a living body. However, 10-OHLA found in adipocere existed also in polymorphonuclear leukocytes, suggesting that this compound metabolized from LTx is closely related to a biological reaction.