Zootermopsis angusticollis

Termites contain high levels of vitamin B in contrast to most other insects (Wakayama et al., 1984). In termites, succinate is converted to methylmalonyl-CoA and serves as the source of the methyl branches (Figure 3.4) (Blomquist et al., 1980 Chu and Blomquist, 1980a, b Halamkar and Blomquist, 1989). The termite Zootermopsis angusticollis converts succinyl-CoA to methylmalonyl-CoA and then to propionate in the gut tract, probably via microorganisms (Guo et al., 1991). The propionate is then apparently transported... 

Chu, A J. and Blomquist, G. J. (1980a). Decarboxylation of tetracosanoic acid to n-tricosane in the termite Zootermopsis angusticollis. Comp. Biochem. Physiol.,... 

The conversion of high specific activity tritium-labeled fatty acids to n-alkanes one carbon unit shorter has been demonstrated in the American cockroach (26) and in the termite Zootermopsis angusticollis (27) in vivo, and in microsomal preparations from the termite (27). Most of the activity in the termite was located in the microsomal fraction and was stimulated two-fold by the addition of ascorbate. 

Blomquist, G. J., Howard, R. W. and McDaniel, C. A. (1978) Biosynthesis of the cuticular hydrocarbons of the termite Zootermopsis angusticollis (Hagen). Incorporation of propionate into dimethylalkanes. Insect Biochem., 9, 371-4. 

In vertebrates, in addition to the main pathway of propionate catabolism (conversion into succinate), alternative pathways may function under conditions when the main pathway is blocked. In the termite Zootermopsis angusticollis a high Bn content apparently is due to the presence of microorganisms in the stomach (Wakayama et al., 1984). There is evidence that vitamin Bn is used by termites for the conversion of succinate to methylmalonate and incorporation of the latter instead of malonyl-CoA into methyl-branched hydrocarbons. Therefore, in termites the direction of carbon flow is the same as in bacteria (from succinate to propionate), but opposite to that found in vertebrates. From the aforesaid it is clear that studying propionic acid fermentation is important not only for understanding the biochemistry of propionic acid bacteria, but of many other organisms, including humans. 

---