Unique structural features define the decarboxylation activity of a CYP152 fatty acid decarboxylase from Lacicoccus alkaliphilus.

Abstract

Cytochrome P450 CYP152s catalyze decarboxylation of fatty acids to generate terminal alkenes, valuable compounds for various industries. Here, we identified, overexpressed, and characterized a new CYP152 enzyme from Lacicoccus alkaliphilus (OleTLA), and compared its biophysical and biochemical properties with the well-studied OleTJE from Jeotgalicoccus sp. 8456. Improved expression protocols gave the highest yields of CYP152 holoenzymes reported to date. OleTLA exhibits twice the catalytic turnover number of OleTJE when using hexadecanoic acid and H2O2 as substrates in 10% (v/v) ethanol. The X-ray structure of OleTLA in complex with icosanoic acid revealed a unique flipped heme and a substrate tunnel configuration which are different than those of other CYP152 decarboxylases. Molecular dynamics simulations revealed that in the presence of EtOH, OleTLA displays structural dynamics which maintain structural interactions better than those of OleTJE. As I178 in OleTLA (equivalent to L176 in OleTJE) shows close interactions with its substrate during simulations, I178L of OleTLA and L176I of OleTJE variants were constructed and investigated for their activities. While L176I in OleTJE caused a significant loss of activity, I178L of OleTLA had activities that were equivalent to or greater than those of the wild-type enzyme, suggesting that overall scaffold of OleTLA is more amenable to mutation than OleTJE. Stopped-flow investigations of OleTLA reactions indicated that EtOH increases the rate constant of Compound I formation. We also identified a new redox partner system, ferredoxin and ferredoxin reductase that can function as effective electron donors for both in vitro and in vivo systems of CYP152s.