and keeping in mind the innate differences in CYP3A4 activation, investigators can better predict drug metabolism and side effects in human CYP3A4 pathways. Turnover Estimates of the turnover rate of human CYP3A4 vary widely. For hepatic CYP3A4, in vivo methods yield estimates of enzyme half-life mainly in the range of 70 to 140 hours, whereas in vitro methods give estimates from 26 to 79 hours. Turnover of gut CYP3A4 is likely to be a function of the rate of enterocyte renewal; an indirect approach based on recovery of activity following exposure to grapefruit juice yields measurements in the 12- to 33-hour range. Technology Due to membrane-bound CYP3A4's natural propensity to conglomerate, it has historically been difficult to study drug binding in both solution and on surfaces. Co-crystallization is difficult since the substrates tend to have a low Kd (between 5-150 μM) and low solubility in aqueous solutions. A successful strategy in isolating the bound enzyme is the functional stabilization of monomeric CYP3A4 on silver nanoparticles produced from nanosphere lithography and analyzed via localized surface plasmon resonance spectroscopy (LSPR). These analyses can be used as a high-sensitivity assay of drug binding, and may become integral in further high-throughput assays utilized in initial drug discovery testing. In addition to LSPR, CYP3A4-Nanodisc complexes have been found helpful in other applications including solid-state NMR, redox potentiometry, and steady-state enzyme kinetics. Ligands Following is a table of selected substrates, inducers and inhibitors of CYP3A4. Where classes of agents are listed, there may be exceptions within the class. Inhibitors of CYP3A4 can be classified by their potency, such as: Strong inhibitor being one that causes at least a 5-fold increase in the plasma AUC values, or more than 80% decrease in clearance. Moderate inhibitor being one that causes at least a 2-fold increase in the plasma AUC values, or 50–80% decrease in clearance. Weak inhibitor being one that causes at least a 1.25-fold but less than 2-fold increase in the plasma AUC values, or 20–50% decrease in clearance. Interactive pathway map See also List of drugs affected by grapefruit References External links PharmGKB: Annotated PGx Gene Information for CYP3A4 CYP3A4 substrate prediction 3 EC 1.14.14