Decarboxylation and Protonation Enigma in the H85Q Mutant of Cytochrome P450OleT

Cytochrome P450OleT (CYP450(OleT)), a member of CYP450 peroxygenases, catalyzes unusual decarboxylation activity. Unlike other members of the peroxygenases family, CYP450OleT possesses a histidine at the 85th position, which was supposed to be the root cause of the decarboxylation activity in CYP450(OleT). This work addresses the His85 ? Gln mutant paradox, where mutation of His-* Gln still shows efficient decarboxylation activity in CYP450OleT. The MD simulation of the H85Q mutant of CYP450(OleT) shows that in the absence of the histidine at the 85th position, an Asp239 plays a similar role via a well-organized water channel. Our simulation shows that such a water channel is vital for the optimal substrate positioning needed for the decarboxylation activity and is gated by the Q85-N242 residue pair. Interestingly, the MD simulation of the WT CYP450BSfi shows a closed channel that blocks access to the Glu236 (analogous residue to Asp239 in CYP450(OleT)), and therefore, CYP450BSfi shows low decarboxylation activity.

Automated summary

CYP450OleT, a member of the CYP450 peroxygenases family, exhibits unique decarboxylation activity. The presence of histidine at position 85 was believed to be responsible for this activity, but mutation to glutamine still maintained efficient decarboxylation. Molecular dynamics simulations revealed that in the absence of histidine, aspartate 239 played a similar role through a well-organized water channel. This channel, regulated by the residue pair of glutamine 85 and asparagine 242, is critical for optimal substrate positioning and decarboxylation activity.