Determination of steroid hydroxylation specificity of an industrial strain Aspergillus ochraceus TCCC41060 by cytochrome P450 gene CYP68J5

Abstract Purpose The use of Aspergillus ochraceus TCCC41060 for synthesis of 11α-OH-ethylgonendione, an important intermediate for synthesis of desogestrel-a major ingredient of the “third-generation” oral contraceptives, is hampered by its low regioselectivity of hydroxylation. In the present study, we sought to characterize gene(s) involved in steroid hydroxylation specificity in strain TCCC41060. Methods Taking advantage of the fact that expression of the 11α-hydroxylase, a member of the cytochrome P450 family, is highly induced by steroid substrates, we combined RNA-seq, qRT-PCR, and yeast functional expression to search for responsible steroid hydroxylase gene(s). Results Two highly inducible P450 genes (CYP68L8 and CYP68J5) were isolated and recombinant yeast cells expressing CYP68J5 were capable of 11α-hydroxylating both 16,17α-epoxyprogesterone and D-ethylgonendione. Disruption of CYP68J5 in strain TCCC41060 resulted in complete loss of hydroxylation activities towards D-ethylgonendione, indicating that CYP68J5 was solely responsible for hydroxylation activity on D-ethylgonendione in TCCC41060. Conclusion The above results demonstrated that low hydroxylation specificity of CYP68J5 on D-ethylgonendione fully accounted for high by-product contents in TCCC41060, thus pointing to a strategy to engineer 11α-hydroxylase variants with higher hydroxylation specificity.