Calreticulin transacetylase: a novel enzyme-mediated protein acetylation by acetoxy derivatives of 3-alkyl-4-methylcoumarins.

Our earlier investigations culminated in the discovery of a unique membrane-bound enzyme Calreticulin transacetylase (CRTAase) in mammalian cells catalyzing the transfer of acetyl group from polyphenolic acetates (PAs) to certain functional proteins viz. Glutathione S-transferase (GST), NADPH Cytochrome c reductase and Nitric oxide synthase (NOS) resulting in the modulation of their biological activities. In order to develop SAR study, herein, we studied the influence of alkyl group at C-3 position of acetoxy coumarins on the CRTAase activity. The alkylated acetoxy coumarins lead to inhibition of catalytic activity of GST, and ADP induced platelet aggregation by the way of activation of platelet Nitric oxide synthase (NOS). Furthermore, the increase in size of the coumarin C-3 alkyl group was found to decrease the CRTAase activity.