# Identification of New Substrates and Inhibitors of Human CYP2A7

## TL;DR

This study identifies new substrates and inhibitors for the human CYP2A7 enzyme and compares two of its variants.

## Contribution

The study introduces new substrates and inhibitors for CYP2A7 and compares the enzymatic properties of two CYP2A7 variants.

## Key findings

- Both CYP2A7 variants hydroxylate diclofenac but do not act on standard CYP2A6 substrates like nicotine.
- Ketoconazole, 1-benzylimidazole, and letrozole were identified as CYP2A7 inhibitors.
- In silico studies were used to understand activity differences between the two CYP2A7 variants on specific substrates.

## Abstract

CYP2A7 is one of the most understudied human cytochrome P450 enzymes and its contributions to either drug metabolism or endogenous biosynthesis pathways are not understood, as its only known enzymatic activities are the conversions of two proluciferin probe substrates. In addition, the CYP2A7 gene contains four single-nucleotide polymorphisms (SNPs) that cause missense mutations and have minor allele frequencies (MAFs) above 0.5. This means that the resulting amino acid changes occur in the majority of humans. In a previous study, we employed the reference standard sequence (called CYP2A7*1 in P450 nomenclature). For the present study, we created another CYP2A7 sequence that contains all four amino acid changes (Cys311, Glu169, Gly479, and Arg274) and labeled it CYP2A7-WT. Thus, it was the aim of this study to identify new substrates and inhibitors of CYP2A7 and to compare the properties of CYP2A7-WT with CYP2A7*1. We found several new proluciferin probe substrates for both enzyme variants (we also performed in silico studies to understand the activity difference between CYP2A7-WT and CYP2A7*1 on specific substrates), and we show that while they do not act on the standard CYP2A6 substrates nicotine, coumarin, or 7-ethoxycoumarin, both can hydroxylate diclofenac (as can CYP2A6). Moreover, we found ketoconazole, 1-benzylimidazole, and letrozole to be CYP2A7 inhibitors.