1. Introduction
Fatty acids play very important and diverse roles in living organisms, such as signal transduction, energy management and maintaining structural integrity to the normal metabolic process. Fatty acid synthases (FAS) are widely found in prokaryotes and eukaryotes, although their structures and functions vary. Fatty acids play a very important role in keeping the metabolic functions normal and are primary metabolites synthesized by a system of complex and tightly controlled biosynthetic machinery (Liu et al ., 2010). Bacteria and plants have type II FAS by which fatty acid synthesis is performed by a set of individual enzymes (White et al ., 2005). Type I FAS, found in animals and fungi, consist of huge molecular assemblies with separate catalytic domains to stitch on the designated fatty acid synthesis, with each catalytic domain acting as unique enzyme (Maier et al ., 2010; Wakil, 1989). In both type I and type II FAS, there is a common acyl carrier protein (ACP) acting as the mobile domain, shuttling the intermediate fatty acid substrates to various catalytic sites.
Studies have identified that FAS can be a promising drug target for cancer (Chalbos et al., 1987; Kuhajda et al ., 1994; Migitaet al ., 2009; Vazquez-Martin et al ., 2008; Wang et al ., 2004). Inhibition of FAS might lead to apoptosis of cancer cells (Zhou et al ., 2003; Deepa et al ., 2013). Since FAS is associated with mycolic acid biosynthesis it could be a TB drug target (Bhatt et al., 2007), with low possibility of drug resistance and toxicity due to the difference in the FAS systems of human and bacteria (Gago et al ., 2011).
There are many molecules that target FAS, like Epigallocatechin, Cerulenin, Orlistat, Pyrimidine, Triclosan, C75, CM55 etc., differing in modes of action and eliciting severe side effects (Brusselmans et al ., 2003; Moche et al ., 1999; Kridel et al ., 2004; Loftus et al ., 2000; Liu et al ., 2002; Rendina et al ., 2005; Tadao et al ., 1974). Hence, new FAS inhibitors are in demand.
Marine microbial sources have become one of the major focuses of research for identifying new chemical entities with diverse biological activities. Cyanobacteria are known to produce molecules with diverse pharmacological properties (Wijffels et al ., 2013; Dixit et al ., 2013). In this study, a FAS inhibitor was successfully isolated from the marine cyanobacteria, Phormidium ambiguum  which could form a lead molecule for drugs against many diseases ranging from cancer to TB.