Refining the plant steroid hormone biosynthesis pathway

Many of the biochemical conversions in plant steroid hormone biosynthesis are catalysed by cytochrome P450 enzymes (CYPs or P450s). A recent paper by Toshiyuki Ohnishi et al. (2006) indicates the role of CYP90C1 and CYP90D1 in the synthesis of the most bioactive plant steroid hormone, brassinolide. These results highlight the need for refining the brassinolide biosynthesis pathway.