Squalene hopene cyclases and oxido squalene cyclases: potential targets for regulating cyclisation reactions.

Squalene hopene cyclases (SHC) convert squalene, the linear triterpene to fused ring product hopanoid by the cationic cyclization mechanism. The main function of hopanoids, a class of pentacyclic triterpenoids in bacteria involves the maintenance of membrane fluidity and stability. 2, 3-oxido squalene cyclases are functional analogues of SHC in eukaryotes and both these enzymes have fascinated researchers for the high stereo selectivity, complexity, and efficiency they possess. The peculiar property of the enzyme squalene hopene cyclase to accommodate substrates other than its natural substrate can be exploited for the use of these enzymes in an industrial perspective. Here, we present an extensive overview of the enzyme squalene hopene cyclase with emphasis on the cloning and overexpression strategies. An attempt has been made to explore recent research trends around squalene cyclase mediated cyclization reactions of flavour and pharmaceutical significance by using non-natural molecules as substrates.

Myo-D-inositol Trisphosphate Signalling in Oomycetes.

Oomycetes are pathogens of plants and animals, which cause billions of dollars of global losses to the agriculture, aquaculture and forestry sectors each year. These organisms superficially resemble fungi, with an archetype being Phytophthora infestans, the cause of late blight of tomatoes and potatoes. Comparison of the physiology of oomycetes with that of other organisms, such as plants and animals, may provide new routes to selectively combat these pathogens. In most eukaryotes, myo-inositol 1,4,5 trisphosphate is a key second messenger that links extracellular stimuli to increases in cytoplasmic Ca2+, to regulate cellular activities. In the work presented in this study, investigation of the molecular components of myo-inositol 1,4,5 trisphosphate signaling in oomycetes has unveiled similarities and differences with that in other eukaryotes. Most striking is that several oomycete species lack detectable phosphoinositide-selective phospholipase C homologues, the enzyme family that generates this second messenger, but still possess relatives of myo-inositol 1,4,5 trisphosphate-gated Ca2+-channels.