Comparative structural and functional studies of acid ceramidase and acid ceramidase-like proteins using biophysical and computational techniques

Abstract

We report here the extensive work carried out on two essential lysosomal enzymes acid ceramidase (AC, EC 3.5.1.23) from zebrafish (Danio rerio), Caenorhabditis elegans and acid ceramidase-like protein (N-acylethanolamine hydrolyzing acid amidase (NAAA), EC 3.5.1.4) from mouse (Mus musculus) and Micromonas commoda (strain RCC299) (Picoplanktonic green alga. These enzymes belong to the N-terminal nucleophile hydrolase superfamily, which is functionally identified as amidases. Based on the presence of Nterminal residue Cys, which acts as a nucleophile, the superfamily classified into N-terminal cysteine nucleophile (NtCn) hydrolases. Being members of Ntn-hydrolase superfamily ACs and NAAAs share a common (αββα) Ntn structural fold and similar catalytic mechanism. Both enzymes are heterodimers and form homodimer assemblies of heterodimer assemblies. AC catalyzes the degradation of ceramide by hydrolyzing the amide bond in ceramide into sphingosine and free fatty acid. NAAA catalyzes the degradation of N-Acylethanolamine (NAE) by hydrolyzing the amide bond in NAE into ethanolamine and free fatty acid. AC and NAAA are glycoprotein and undergo post-translational processing to mature as an active form. The detailed work presented in the thesis underpins the biochemical and structural characterization along with computational analysis of AC and NAAA.