Exhibits low testosterone 6-beta-hydroxylase activity. an organic molecule + O2 + reduced [NADPH--hemoprotein reductase] = an alcohol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Additional isoforms seem to exist. Highest expression level in prostate. Also expressed in liver, kidney, pancreas, fetal liver and fetal skeletal muscle. By rifampicin. At protein level, three alleles are known: CYP3A43*1, CYP3A43*2 and CYP3A43*3. The sequence shown is that of CYP3A43*1, which is the most frequent allele. The allele CYP3A43*2 is likely to be non-functional. Chimeric transcripts, characterized by CYP3A43 exon 1 joined at canonical splice sites to distinct sets of CYP3A4 or CYP3A5 exons, have been detected. All are possibly produced by trans-splicing. CYP3A43-CYP3A4 chimeric transcripts exist in 3 different combinations: CYP3A43 exon 1 joined in frame to CYP3A4 exons 2-13, CYP3A43 exon 1 joined in frame to CYP3A4 exons 4-13 and CYP3A43 exon 1 joined in frame to CYP3A4 exon 7-13. The longest chimeric isoform (CYP3A43 exon 1 joined to CYP3A4 exons 2-13) exhibits 6-beta-hydroxylase activity, while a shorter isoform (CYP3A43 exon 1 joined to CYP3A4 exons 4-13) does not. CYP3A43-CYP3A5 chimeric transcripts exist in 2 different combinations: CYP3A43 exon 1 joined in frame to CYP3A5 exon 11-13 and CYP3A43 exon 1 joined in frame to CYP3A5 exon 12-13. All chimeric transcripts are expressed at very low levels in the liver (PubMed:11726664). May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the cytochrome P450 family. CYP3A43 alleles