Fig. 7 in Comparison of glucosinolate diversity in the crucifer tribe Cardamineae and the remaining order Brassicales highlights repetitive evolutionary loss and gain of biosynthetic steps

Fig. 7. Stages in the biosynthesis of parent glucosinolates (GSLs) without (A) or with (B) chain elongation of the precursor standard amino acid. A CYP79 enzyme catalyzes the first reaction in the known (cytosolic) core structure biosynthesis pathways, followed by six enzymatic steps constituting the remaining core structure biosynthesis pathway, abbreviated "r. csb". For GSLs without chain elongation (A), the CYP79 catalyzed reaction is the committed step. For GSLs needing chain elongation (B), however, the chain elongation machinery as well as transport ("T") across the chloroplast membrane and reversible amino transferase reactions collectively constitute the committed step, illustrated as a box-like reaction arrow containing the individual reactions.