Biosynthesis of lovastatin and related metabolites formed by fungal iterative PKS enzymes.

The fungal polyketide lovastatin is a cholesterol lowering agent that is an immediate precursor to a multi-billion dollar drug, simvastatin (Zocor). Lovastatin is produced by an iterative type I polyketide synthase known as LovB and a partner enoyl reductase (LovC). There is evidence that a Diels-Alderase enzyme activity is utilized in its biosynthesis. This review examines the biosynthesis of lovastatin, as well as of compactin, equisetin, cytochalasins, and solanapyrones, which are other structurally related polyketides that appear to utilize a Diels-Alderase.

Photobleaching kinetics of optically trapped multilamellar vesicles containing verteporfin using two-photon excitation section sign.

Two-photon excitation photodynamic therapy (TPE-PDT) is being developed as an improved treatment for retinal diseases. TPE-PDT has advantages over one-photon PDT, including lower collateral damage to healthy tissue and more precise delivery of PDT. As with one-photon PDT, there can be local photochemical depletion of oxygen during TPE-PDT. Here, we investigate model systems and live cells to measure local photosensitizer photobleaching and through it, infer local oxygen consumption in therapeutic volumes of the order 1 microm3. Multilamellar vesicles (MLV) and African green monkey kidney (CV-1) cells were used to study the TPE photobleaching dynamics of the photosensitizer, Verteporfin. It was found that in an oxygen-rich environment, photobleaching kinetics could not be modeled using a mono-exponential function, whereas in hypoxic conditions a mono-exponential decay was adequate to represent photobleaching. A biexponential was found to adequately model the oxygen-rich conditions and it is hypothesized that the fast part of the decay is oxygen-dependent, whereas the slower rate constant is largely oxygen-independent. Photobleaching recovery studies in the CV-1 cells support this hypothesis.