UC Irvine

Heme enzymes are ubiquitous in nature with several biological functions encompassing cytoprotection, neuronal signaling, biosynthesis of natural products and xenobiotic detoxification. This unique functionality of each heme enzyme is because of its structure. Thus, the aim of this dissertation is to probe structure-function relationships of these enzymes, understand the active site chemistry and employ this information for pharmaceutical applications. This is achieved by studying two different heme enzyme systems – nitric oxide synthase (NOS) and a few cytochromes P450. NOS is involved in the production of NO which provides antibiotic resistance to various Gram-positive bacteria (bNOS) like methicillin-resistant Staphylococcus aureus (MRSA) and acts as a signaling molecule in mammals (mNOS). Inhibition of bNOS decreases NO and makes MRSA more susceptible to antibiotics and host-induced oxidative stress. A collaborative work to design efficient and bNOS selective small molecules to treat MRSA infection is described here. Various natural products have antibiotic properties and require cytochromes P450 for their biosynthesis. The aim is to structurally and functionally characterize two P450s from Streptomyces involved in biosynthesis of antibiotics. This will help to understand protein-substrate interactions involved in the biosynthesis of these antibiotics. Eventually, this will assist in engineering enzymes to generate novel antibiotics with greater efficacy and specificity. P450cam (CYP101A1) is one of the most studied P450s and consumes camphor as a source of carbon/energy. This dissertation concludes with a study to better understand structural and functional aspects of another camphor degrading P450 from Pseudomonas sp. strain TCU-HL1 which shares about 86% sequence identity with P450cam.