New assumptions about oxidative processes involved in steroid hormone biosynthesis: Is the role of cytochrome P-450-activated dioxygen limited to hydroxylation reactions or are dioxygen insertion reactions also possible?

Gene expression in diapause-destined embryos of the crustacean, Artemia franciscana

“…Equally vague is whether hormone synthesis occurs in mature females versus embryos, if hormones are activated or inhibited by steroid dehydrogenase, and the cell processes influenced by hormones. Oxidized and reduced nicotinamide are likely to fluctuate in amount as metabolism changes during diapause, supplying triggers for modification of steroid dehydrogenase and cytochrome P450, an NADPH-requiring enzyme capable of irreversible steroid modification (Agarwal and Auchus, 2005;Lieberman et al, 2005;Bishop et al, 2006) and for which mRNA increases during Artemia diapause.…”

Muriceanol, a 24(28)‐Epoxide Sterol Link in the Carbon Flux Toward Side‐Chain Dealkylation of Sterols

“…However, since sterols with hydroxylated side chain are unusual in microalgae, [14,15] coral should be responsible for the 22-hydroxylation, but whether the oxygen atoms of the 22-hydroxy group and the oxirane ring of 1 arise from the same oxygen molecule or from separate molecules is an open question [16] and encourages biosynthetic speculations. Insertion of biologically excited singlet oxygen O 2 ( 1 ∆g) in a 1,4-diene 7 leading to 8 (path b) in an overall 1,4-addition, followed by stereospecific endoperoxide cleavage should also be considered as an alternative pathway [17] for muriceanol (1). The regioselectivity of the oxygenated sidechain substituents appears to be compatible with this mechanism and its stereospecificity suggests the addition of singlet oxygen is enzymatically catalyzed rather than photochemically produced.…”

The generally accepted version of steroidogenesis is not free of uncertainties: Other tenable and possibly superior renditions may be invented

“…chemically plausible, renditions of steroidogenic processes that are different from those pictured in GAV [1][2][3][4][5].…”

“…In several previous essays [1][2][3][4][5], the relevant experimental "facts" and the interpretations derived from them about steroidogenic processes occurring in vivo were examined. These analyses led to the conclusion that the experimentally derived evidence upon which the GAV is based does not lead to interpretations about in vivo processes that are unique and inerrant.…”

“…Since the GAV is replete with uncertainties, the invention of other hypothetical, but tenable versions [1][2][3][4][5], is in keeping with the continuing search for truth. This search is not a purely academic, arcane effort of interest only to biochemists.…”