Investigations on the mechanism of adipocere formation and its relation to other biochemical reactions.

In the adipocere, which is one of the 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 shown 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 bacterial enzymes. 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. It turned out that 10-OHFA was synthesized only from fatty acids possessing cis-9-unsaturation. It was also shown that 10-OHFAs were converted to the corresponding 10-OXOFAs but the 10-OXO compounds were inactive as substrates. Furthermore, it was found that 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-OHODA) from linoleic acid in some kinds of adipocere. Recently, 10-epoxy-12-octadecenoic acid (leukotoxin, LTx), which is one of the lipid peroxides, was found not only in rice plants but in polymorphonuclear leukocytes. Since LTx was found in leukocytes related to inflammatory response, interest has been focused on its involvement, not only in the basic mechanism of biological defense, but also on the mechanism of shock as a vasoactive substance. A postmortem change itself is only remotely associated with a phenomenon in a living body. However, 10-OHODA found in adipocere seemed to exist also in polymorphonuclear leukocytes, suggesting that this compound might be closely related to a biological reaction.