CYP2B6 is mainly expressed in the liver that has been thought historically to play an insignificant role in human drug metabolism. However, increased interest in this enzyme has been stimulated by the discovery of polymorphic and ethnic differences in CYP2B6 expression, identification of additional substrates for CYP2B6, and evidence for co-regulation with CYP3A4. This paper updates our knowledge about the structure, function, regulation and polymorphism of CYP2B6. CYP2B6 can metabolise approximately 8% of clinically used drugs (n > 60), including cyclophosphamide, ifosfamide, tamoxifen, ketamine, artemisinin, nevirapine, efavirenz, bupropion, sibutramine, and propofol. CYP2B6 is one of the CYP enzymes that bioactivate several procarcinogens and toxicants. This enzyme also metabolizes arachidonic acid, lauric acid, 17beta-estradiol, estrone, ethinylestradiol, and testosterone. Typical substrates of CYP2B6 are non-planar molecules, neutral or weakly basic, highly lipophilic with one or two hydrogen-bond acceptors. The crystal structure of CYP2B6 has not been resolved, while several pharmacophore and homology models of human CYP2B6 have been reported. Human CYP2B6 is closely regulated by constitutive androstane receptor (CAR/NR1I3) which can activate CYP2B6 expression upon ligand binding. Pregnane X receptor and glucocorticoid receptor also play a role in the regulation of CYP2B6. Induction of CYP2B6 may partially explain some clinical drug interactions observed. For example, coadministered carbamazepine decreases the systemic exposure of bupropion. There is a wide interindividual variability in the expression and activity of CYP2B6. Such a large variability is probably due to effects of genetic polymorphisms and exposure to drugs that are inducers or inhibitors of CYP2B6. To date, at least 28 allelic variants and some subvariants of CYP2B6 (*1B through *29) have been described and some of them have been shown to have important functional impact on drug clearance and drug response. For example, the efavirenz plasma levels in African-American subjects with the CYP2B6 homozygous 516T/T genotype are approximately 3-fold higher than individuals carrying the homozygous G/G genotype. The CYP2B6 516T/T genotype is associated with 1.7-fold greater plasma levels of nevirapine in HIV-infected patients. Smokers with the 1459C>T (R487C) variant of CYP2B6 may be more vulnerable to abstinence symptoms and relapse following treatment with bupropion as a smoking cessation agent. Further studies in the structure, function, regulation and polymorphism of CYP2B6 are warranted.

Scarlet fever is one of a variety of diseases caused by group A Streptococcus (GAS). During 2011, a scarlet fever epidemic characterized by peak monthly incidence rates 2.9–6.7 times higher than those in 2006–2010 occurred in Beijing, China. During the epidemic, hospital-based enhanced surveillance for scarlet fever and pharyngitis was conducted to determine characteristics of circulating GAS strains. The surveillance identified 3,359 clinical cases of scarlet fever or pharyngitis. GAS was isolated from 647 of the patients; 76.4% of the strains were type emm12, and 17.1% were emm1. Almost all isolates harbored superantigens speC and ssa. All isolates were susceptible to penicillin, and resistance rates were 96.1% to erythromycin, 93.7% to tetracycline, and 79.4% to clindamycin. Because emm12 type GAS is not the predominant type in other countries, wider surveillance for the possible spread of emm12 type GAS from China to other countries is warranted.

CYP1A2 is one of the major CYPs in human liver ( approximately 13%) and metabolises a variety of clinically important drugs, such as clozapine, lidocaine, theophylline, tacrine, and leflunomide. CYP1A2 is one of the major enzymes that bioactivate a number of procarcinogens and thus induction of CYP1A2 may increase the carcinogenicity of these compounds. This enzyme also metabolizes several important endogenous compounds including steroids, retinols, melatonin, uroporphyrinogen and arachidonic acid. In the recently published crystal structure of CYP1A2 in complex with alpha-naphthoflavone, its compact active site is closed without clear solvent or substrate access channels. Not surprisingly, CYP1A2 has a relatively small volume of the active site cavity of 375 A(3), which is 44.2% larger than that of CYP2A6 (260 A(3)), but much smaller than that of CYP3A4 (1385 A(3)) and 2C8 (1438 A(3)). Generally, CYP1A2 substrates contain planar ring that can fit the narrow and planar active site of the enzyme. Like many of other CYPs, CYP1A2 is subject to induction and inhibition by a number of compounds. Similar to CYP1A1 and 1B1, CYP1A2 is primarily regulated by the aromatic hydrocarbon receptor (AhR), a ligand-activated transcription factor and a basic helix-loop-helix protein belonging to the Per-Arnt-Sim family of transcription factors. Knockout of Cyp1a2 in mice has provided a very useful tool for the functional investigation of this gene. Further studies are needed to explore the clinical and toxicological significance of CYP1A2.

The MPAL cardioplegia formula was associated with better myocardial protective effects.