The X-Ray Crystal Structure of the Human Mono-Oxygenase Cytochrome P450 3A5-Ritonavir Complex Reveals Active Site Differences between P450s 3A4 and 3A5.

The contributions of cytochrome P450 3A5 to the metabolic clearance of marketed drugs is unclear, but its probable role is to augment the metabolism of several drugs that are largely cleared by P450 3A4. Selective metabolism by 3A4 is often a concern in drug development owing to potential drug-drug interactions and the variability of 3A4 and 3A5 expression. The contribution of P450 3A5 to these clearance pathways varies between individuals owing to genetic differences and similarities and differences in the metabolic properties of 3A5 compared with 3A4.

Heme-thiolate sulfenylation of human cytochrome P450 4A11 functions as a redox switch for catalytic inhibition.

Cytochrome P450 (P450, CYP) 4A11 is a human fatty acid ω-hydroxylase that catalyzes the oxidation of arachidonic acid to the eicosanoid 20-hydroxyeicosatetraenoic acid (20-HETE), which plays important roles in regulating blood pressure regulation. Variants of P450 4A11 have been associated with high blood pressure and resistance to anti-hypertensive drugs, and 20-HETE has both pro- and antihypertensive properties relating to increased vasoconstriction and natriuresis, respectively. These physiological activities are likely influenced by the redox environment, but the mechanisms are unclear.

20-Hydroxyeicosatetraenoic Acid (HETE)-dependent Hypertension in Human Cytochrome P450 (CYP) 4A11 Transgenic Mice: NORMALIZATION OF BLOOD PRESSURE BY SODIUM RESTRICTION, HYDROCHLOROTHIAZIDE, OR BLOCKADE OF THE TYPE 1 ANGIOTENSIN II RECEPTOR.

Male and female homozygous 129/Sv mice carrying four copies of the human cytochrome P450 4A11 gene (CYP4A11) under control of its native promoter (B-129/Sv-4A11(+/+)) develop hypertension (142 ± 8 versus 113 ± 7 mm Hg systolic blood pressure (BP)), and exhibit increased 20-hydroxyeicosatetraenoic acid (20-HETE) in kidney and urine. The hypertension is reversible by a low-sodium diet and by the CYP4A inhibitor HET0016. B-129/Sv-4A11(+/+) mice display an 18% increase of plasma potassium (p < 0.

Crystal structure of human cytochrome P450 2D6 with prinomastat bound.

Human cytochrome P450 2D6 contributes to the metabolism of >15% of drugs used in clinical practice. This study determined the structure of P450 2D6 complexed with a substrate and potent inhibitor, prinomastat, to 2.85 Å resolution by x-ray crystallography.

Genistein, resveratrol, and 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside induce cytochrome P450 4F2 expression through an AMP-activated protein kinase-dependent pathway.

Activators of AMP-activated protein kinase (AMPK) increase the expression of the human microsomal fatty acid ω-hydroxylase CYP4F2. A 24-h treatment of either primary human hepatocytes or the human hepatoma cell line HepG2 with 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), which is converted to 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranosyl 5'-monophosphate, an activator of AMPK, caused an average 2.5- or 7-fold increase, respectively, of CYP4F2 mRNA expression but not of CYP4A11 or CYP4F3, CYP4F11, and CYP4F12 mRNA.

Structural characterization of the complex between alpha-naphthoflavone and human cytochrome P450 1B1.

The atomic structure of human P450 1B1 was determined by x-ray crystallography to 2.7 Å resolution with α-naphthoflavone (ANF) bound in the active site cavity. Although the amino acid sequences of human P450s 1B1 and 1A2 have diverged significantly, both enzymes exhibit narrow active site cavities, which underlie similarities in their substrate profiles.

Opposing roles of peroxisome proliferator-activated receptor alpha and growth hormone in the regulation of CYP4A11 expression in a transgenic mouse model.

CYP4A11 transgenic mice (CYP4A11 Tg) were generated to examine in vivo regulation of the human CYP4A11 gene. Expression of CYP4A11 in mice yields liver and kidney P450 4A11 levels similar to those found in the corresponding human tissues and leads to an increased microsomal capacity for omega-hydroxylation of lauric acid. Fasted CYP4A11 Tg mice exhibit 2-3-fold increases in hepatic CYP4A11 mRNA and protein, and this response is absent in peroxisome proliferator-activated receptor alpha (PPARalpha) null mice.

Human cytochrome p450 family 4 enzymes: function, genetic variation and regulation.

The microsomal cytochrome P450 (CYP) family 4 monooxygenases are the major fatty acid omega-hydroxylases. These enzymes remove excess free fatty acids to prevent lipotoxicity, catabolize leukotrienes and prostanoids, and also produce bioactive metabolites from arachidonic acid omega-hydroxylation. In addition to endogenous substrates, recent evidence indicates that CYP4 monooxygenases can also metabolize xenobiotics, including therapeutic drugs.

Regulation of human cytochrome P450 4F2 expression by sterol regulatory element-binding protein and lovastatin.

This report provides the first evidence that human P450 4F2 (CYP4F2) is induced by statins, which are widely used to treat hypercholesterolemia. Real time PCR and immunoblots indicate that lovastatin treatment increases expression of the endogenous CYP4F2 gene in human primary hepatocytes and HepG2 cells. The effects of lovastatin on gene expression are often mediated through sterol regulatory element-binding proteins (SREBPs).

Conditional regulation of the human CYP4X1 and CYP4Z1 genes.

Cytochrome P450 genes (CYPs) encoding two new subfamilies designated CYP4X1 and CYP4Z1 were identified in the human genome and the Expressed Sequence Tags database. Partial cDNAs encoding both P450s were isolated from human kidney and used to determine tissue distribution. CYP4X1 was predominantly expressed in trachea and aorta, whereas CYP4Z1 mRNA was preferentially expressed in mammary tissue.

Regulation of P450 4A expression by peroxisome proliferator activated receptors.

The induction of P450 4A enzymes by peroxisome proliferators (PPs) and fatty acids is mediated by the peroxisome proliferator activated receptor alpha (PPAR alpha) that binds to response elements in target genes as a heterodimer with the retinoid X receptor (RXR). The consensus sequence recognized by PPAR/RXR heterodimers, contains an imperfect direct repeat of two nuclear receptor binding motifs separated by a single nucleotide. This repeat is preceded by a conserved A/T rich sequence that is required for function.

Differential regulation of human CYP4A genes by peroxisome proliferators and dexamethasone.

HepG2 cells that stably overexpress PPARalpha were used to examine the regulation of the two known human CYP4A genes by Wy14643. Specific PCR amplification across intron 5 and restriction endonuclease analysis indicated that HepG2 cells possess genes corresponding to both the CYP4A11 cDNA and a more recently characterized gene, CYP4A22, that exhibits 95% identity to CYP4A11 in the coding region. These are unlikely to represent alleles because both genes were present in DNA samples from 100 of 100 individuals.