Conclusion

Abstract

The known inhibitory effects of purine, pyrimidine and nucleoside analogues have been discussed in the preceding chapters. A general observation is that most of the analogues can participate in many reactions of their normal counterparts and may inhibit at multiple loci. Substrate or inhibitory activity of a particular analogue on a specific enzymic reaction is obtained mainly from studies with the isolated enzyme. In certain instances a correlation between in vitro and in vivo observations is possible. A major problem encountered, however, is the lack of cohesive and systematic studies. This is obviously a result of the use of a variety of biological systems in various laboratories interested in different aspects of inhibitor actions. The biological systems used vary from bacteria to the more complex tissues of vertebrates. Thus, the problem is not just the questionable validity of the extrapolation of in vitro data to living cells, but also the existence of variations in the enzymes, nucleic acids, and other cellular components of the species investigated. For these reasons, the present compilation, particularly the outline formats, should be viewed with considerable reservation. It should also be remembered that additional inhibitory effects, which are as yet unknown, may have equal or even more importance in living cells.