Algorithm-aided engineering of aliphatic halogenase WelO5* for the asymmetric late-stage functionalization of soraphens.

Late-stage functionalization of natural products offers an elegant route to create novel entities in a relevant biological target space. In this context, enzymes capable of halogenating sp3 carbons with high stereo- and regiocontrol under benign conditions have attracted particular attention. Enabled by a combination of smart library design and machine learning, we engineer the iron/α-ketoglutarate dependent halogenase WelO5* for the late-stage functionalization of the complex and chemically difficult to derivatize macrolides soraphen A and C, potent anti-fungal agents. While the wild type enzyme WelO5* does not accept the macrolide substrates, our engineering strategy leads to active halogenase variants and improves upon their apparent kcat and total turnover number by more than 90-fold and 300-fold, respectively. Notably, our machine-learning guided engineering approach is capable of predicting more active variants and allows us to switch the regio-selectivity of the halogenases facilitating the targeted analysis of the derivatized macrolides' structure-function activity in biological assays.

Regioselective ω-hydroxylation of medium-chain n-alkanes and primary alcohols by CYP153 enzymes from Mycobacterium marinum and Polaromonas sp. strain JS666.

The oxofunctionalization of saturated hydrocarbons is an important goal in basic and applied chemistry. Biocatalysts like cytochrome P450 enzymes can introduce oxygen into a wide variety of molecules in a very selective manner, which can be used for the synthesis of fine and bulk chemicals. Cytochrome P450 enzymes from the CYP153A subfamily have been described as alkane hydroxylases with high terminal regioselectivity. Here we report the product yields resulting from C(5)-C(12) alkane and alcohol oxidation catalyzed by CYP153A enzymes from Mycobacterium marinum (CYP153A16) and Polaromonas sp. (CYP153A P. sp.). For all reactions, byproduct formation is described in detail. Following cloning and expression in Escherichia coli, the activity of the purified monooxygenases was reconstituted with putidaredoxin (CamA) and putidaredoxin reductase (CamB). Although both enzyme systems yielded primary alcohols and α,ω-alkanediols, each one displayed a different oxidation pattern towards alkanes. For CYP153A P. sp. a predominant ω-hydroxylation activity was observed, while CYP153A16 possessed the ability to catalyze both ω-hydroxylation and α,ω-dihydroxylation reactions.

Expression, purification and characterization of two Clostridium acetobutylicum flavodoxins: potential electron transfer partners for CYP152A2.

Two flavodoxin genes from Clostridium acetobutylicum, CacFld1 (CAC0587) and CacFld2 (CAC3417), were expressed in Escherichia coli and investigated for their ability to support activity of CYP152A2, a fatty acid hydroxylase from C. acetobutylicum. E. coli flavodoxin reductase (FdR) was used as a redox partner, since flavodoxin reductase CacFdR (CAC0196) from C. acetobutylicum could not be purified in a functional form. CacFld1 was shown to accept electrons from FdR and transfer them to CYP152A2. Since H2O2 was generated by uncoupling at different stages of the reconstituted electron transfer chain, catalase was used as H2O2 scavenger in order to exclude peroxygenation by CYP152A2. The reconstituted P450 system with CacFld1 and FdR oxidized myristic acid with a K(M) of 137 µM and a k(cat) of 36 min⁻¹. Furthermore, the hydroxylase activity of CYP152A2 towards myristic acid with CacFld1 was 17-fold higher than without CacFld1. Along with CYP152A2 and a physiological flavodoxin reductase, CacFld1 is therefore likely to be involved in oxygen detoxification in C. acetobutylicum. Flavodoxin CacFld2 did not accept electrons from NADPH-reduced FdR, though it cannot be excluded as a candidate redox partner for CYP152A2 in the presence of an appropriate physiological reductase.