EFFECTS OF THIAMINE PROPYL DISULFIDE ON TRYPTOPHAN PYRROLASE IN RATS

Abstract

The formation of complex between protein and thiamine propyl disulfide (TPD) has been studied by many investigators. Higher radioactivity in rats treated with TPD-S³⁵ (outer) was found in blood (1), and when venous blood of normal healthy rabbit was incubated with TPD-S³⁵ (outer), the radioactivity was concentrated in serum albumin fraction (2). As illustrated in Fig. 1, TPD contains S-S bond which is reduced to produce both propylmercapto moiety and thiol type of thiamine. Utsumi et al. (3) indicated the formation of complex between albumin and propylmercapto moiety dissociated from TPD, and their successive paper (4) described binding of TPD to bovine serum albumin. Reduction of TPD in incubation with blood cell was responsible for SH groups in blood (5), and Kawasaki el al. (6) suggested the binding between TPD and SH enzymes, papain and alcohol dehydrogenase. On the other hand, recent studies by Maeno and Feigelson (7) have shown the chemical properties of the reductive activation of liver tryptophan pyrrolase (TP) by ascorbate, GSH and dithiothreitol, and implicated that one or more SH groups were involved in TP as binding site for tryptophan. In the previous paper (8), six thiamine derivatives, i.e., thiamine-mono, -di and -triphosphate, S-benzoylthiamine-mono, -di and -tri phosphate were used to examine their effects on TP in the mechanism of energy dependent activation by ATP-Mn⁺⁺ system reported by Pitot and Cho (9) and no significant effects were observed. It seemed possible to speculate that these phosphates of thiamine or S-benzoylthiamine have little effect on TP because of involving no S-S groups in their molecules. Since preliminary experiments with homogenate showed that effects of TPD on TP varied on pH of the incubation mixture, the purpose of the present study is to investigate the effects of TPD on TP.