Steroid Sulfotransferases

THE discovery that steroids are excreted in urine as conjugates of sulfuric acid was made more than 50 yr ago (1, 2). The enzymes responsible for forming the steroid sulfoconjugates, however, were not initially examined until almost 20 yr later (3–6). After that, interest rose rapidly, resulting in considerable progress for this important and intriguing metabolic process. The importance pertains to the striking change in the physical, chemical, and biological properties that occurs on formation of steroid sulfoconjugates; the fascination relates to the fact that the biological significance of this process, for the most part, remains a conundrum. It is especially enigmatic in steroidogenic tissues such as the adrenal, ovary, and testis. The fact is, 40 yr of investigation, notwithstanding, neither the biochemistry nor the biological import of steroid sulfonation is well understood. The enzymology, although appearing simple in principle, is complex and although interesting functional implications have been put forth, the biology of steroid sulfonation has been difficult to assess and thus remains largely speculative.