Sterol 14alpha-demethylase cytochrome P450 (CYP51), a P450 in all biological kingdoms

Abstract

The CYP51 family is an intriguing subject for fundamental P450 structure/function studies and is also an important clinical drug target. This review updates information on the variety of the CYP51 family members, including their physiological roles, natural substrates and substrate preferences, and catalytic properties in vitro. We present experimental support for the notion that specific conserved regions in the P450 sequences represent a CYP51 signature. Two possible roles of CYP51 in P450 evolution are discussed and the major approaches for CYP51 inhibition are summarized.

Figure 1

Amino acid sequence identity in the CYP51 family. Alignment of 71 sequences was performed using ClustalW 1.82, percentage of amino acid identity was calculated in GeneDoc (2.6). *(number of sequences in the alignment/ percentage of identity). Complete alignment of CYP51 family can be found at the web site https://medschool.mc.vanderbilt.edu/watermanlab/index.php

Figure 2

CYP51 reaction in sterol biosynthesis. D, 24, 25-dihydrolanosterol; L, lanosterol; M, 24-methylenedihydrolanosterol; N, norlanosterol; O, obtusifoliol. *We have found recently that N is likely to be the preferred CYP51 substrate in Trypanosomatidae with the exception of T. cruzi [36]. R₁, alkyl or alkylene group; R₂, C6 or C7 double bond. The dashed line shows a major site of regulation of sterol biosynthesis.

Figure 2

CYP51 reaction in sterol biosynthesis. D, 24, 25-dihydrolanosterol; L, lanosterol; M, 24-methylenedihydrolanosterol; N, norlanosterol; O, obtusifoliol. *We have found recently that N is likely to be the preferred CYP51 substrate in Trypanosomatidae with the exception of T. cruzi [36]. R₁, alkyl or alkylene group; R₂, C6 or C7 double bond. The dashed line shows a major site of regulation of sterol biosynthesis.

Figure 3

Typical spectra of eukaryotic CYP51 (sterol 14α-demethylase from T. cruzi). A, absolute oxidized; B, reduced CO difference; C, type I spectral response to substrate 24-methylenedihydrolanosterol; D, type II spectral response to azole inhibitor ketoconazole.

Figure 4

Conservation in the CYP51 SRS1 and 4. A CYP51 signature is written below the alignment. Phyla-specific residues are shadowed in gray.

Figure 5

Location of the CYP51 signature in the P450 structure. A, upper view, B, distal view. The conserved regions within the B'helix/BC loop and in the I-helix are colored in red. Heme is shown in green.

Figure 6

Mutagenesis of conserved P81 in the B' helix of M. tuberculosis CYP51.