Novel SNPs in Cytochrome P450 Oxidoreductase

Abstract

Cytochrome P450 oxidoreductase (POR) is the single flavoprotein which donates electrons to the microsomal cytochrome P450 enzymes for oxidation of their substrates. In this study, we sequenced all 15 exons and the surrounding intronic sequences of POR in 100 human liver samples to identify novel and confirm known genetic polymorphisms in POR. Thirty-four single nucleotide polymorphisms (SNPs) were identified including 9 in the coding exons (5 synonymous and 4 nonsynonymous), 20 in the intronic regions, and 5 in the 3'-UTR. Of these, 9 were novel SNPs, including three nonsynonymous SNPs, SNH313003 (817733G>C; K49N), SNH313020 (848661C>A; L420M), and SNH313029 (849577T>C; L577P) with minor allele frequencies of 0.005, 0.045, and 0.020, respectively. We also confirmed a previously reported non-synonymous SNP rs1057868 (A503V) as well as five synonymous SNPs (G5G, T29T, P129P, S485S, and S572S) all with allele frequencies similar to those previously reported. Structurally, these polymorphisms occur in different regions: SNH313003 (K49N) in the amino-terminal tail, SNH313020 (L420M) in the connecting domain, SNH313029 (L577P) in the NADPH-binding domain, and rs1057868 (A503V) in the FAD binding domain.

Genetic polymorphisms in cytochrome P450 oxidoreductase influence microsomal P450-catalyzed drug metabolism

“…A503V has been reported in the NCBI dbSNP and has moderate influence on POR activity (69% of wild type) [17]. We first reported K49N, L420M, and L577P [25]. To predict the potential influence of K49N, L420M, and L577P on POR functions, we POR, cytochrome P450 oxidoreductase.…”

“…Of these, 20 were in the introns, five in the 3 0 -UTR, and nine in the exons ( Table 4). Nine of the 34 SNPs were novel polymorphisms recently reported for the first time [25]. Of the nine exonic polymorphisms, five were synonymous polymorphisms (G5G, T29T, P129P, S485S, and S572S) and four were nonsynonymous polymorphisms resulting in amino acid changes at K49N, L420M, A503V, and L577P that had minor allele frequencies of 0.005, 0.045, 0.219, and 0.020, respectively.…”

“…Exonic regions of POR were amplified by PCR from the genomic DNA using forward and reverse primers designed by DS Gene Software (Accelrys, Cambridge, UK). Primer sequences and PCR product sizes have been previously reported by our lab [25]. Primers were synthesized by Integrated DNA Technologies (Coralville, Iowa, USA) and the subsequent PCR reactions were performed using Go Taq DNA Polymerase (Promega, Madison, Wisconsin, USA), with cycling conditions of 951C for 3 min, 40 cycles of 941C for 15 s, 601C for 30 s, and 721C for 45 s, followed by 721C for 5 min.…”

“…It is, however, unclear whether genetic polymorphisms in the POR gene affect P450-catalyzed drug metabolism. Recently, we identified novel SNPs in the POR gene in individuals without POR deficiency [25]. In this report, we performed a comprehensive study to establish correlations of genetic polymorphisms in the POR gene with POR gene expression, POR activity, and POR-assisted P450 activities using a set of human liver tissue samples.…”

Nomenclature for alleles of the cytochrome P450 oxidoreductase gene

“…Many of these were found [1–6] because of their association with steroidogenic disorders and congenital skeletal malformations resembling the phenotype of Antley-Bixler syndrome [7], whereas other alleles have been found as a consequence of sequencing the POR gene in normal unrelated individuals [8,9]. The association of POR variants with clinical phenotypes is the result of POR serving as the major electron donor for cytochrome P450 (CYP) enzymes with important endogenous functions in hormone biosynthesis.…”