Characterization of CrSEX4, a phosphoglucan phosphatase from Chlamydomonas reinhardtii

TORRESI, FLORENCIA; RICORDI, MICAELA; GÓMEZ-CASATI DIEGO; BUSI, MARÍA VICTORIA; MARTÍN, MARIANA

Paraná, Entre Ríos

Congreso; LIV Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2018

Glucan phosphatases have emerged as essential enzymes for normal starch degradation in plants as well as glycogen metabolism in mammals.Arabidopsis thalianaphosphoglucan phosphatases starch excess 4 (SEX4) and like-SEX4 2 (LSF2) and human Laforin are the fundamental representatives of the atypical Dual Specificity Phosphatases (DSPs), which belong to the larger Protein Tyrosine Phosphatase superfamily. To understand the evolution of catalysis and regulation of these enzymes we are studying CrSEX4, a SEX4 homologous protein belonging to the unicellular green algae C. reinhardtii. We constructed a series of mutants by site directed mutagenesis and studied phosphatase activity of the recombinant enzymes as well as their ability to bind polysaccharides. The results led to confirm that C224 is the catalytic cysteine residue. Activity assays with the artificial substrate para-nitrophenylphosphate suggest the presence of a putative second substrate binding site in CrSEX4.