ALGAE ACID PHOSPHATASE AFFECTED BY TEN METALS AND ENZYMATIC PARAMETERS DETERMINATION IN PRESENCE OF MERCURY AND COPPER
Acid phosphatases play important roles in algae metabolism such availability/recycling of inorganic phosphate and autophagic digestive processes. Chemicals released into the environment from agricultural activities and through industrial and urban wastes, may impair algae enzyme activity. The aim of this work was to evaluate the in vitro activation/inhibition effect of ten metals, commonly present as contaminants in soil and water, on the acid phosphatase extracted from the green algae Pseudokirchneriella subcapitata. Results demonstrated that Hg, Al, Mo, Pb, Se and Cd inhibited the enzyme activity in 56.3, 54.5, 30.6, 25.5, 23.1 and 11.5%, respectively. This corresponds to the maximum percentage of effect attained at the metal concentrations tested (0.02–2.0 mM). On the other hand, Cu, Zn, Ni and Cr exhibited an increment on phosphatase activity equal to 95.5, 87.6, 77.6 and 42.8%, respectively. Kinetic parameters values were calculated for the metals that showed highest effects. Thus, Ki (inhibition constant) and Kd (dissociation constant) values equal to 0.0400 and 0.0016 mM were determined for Hg and Cu, respectively. A non-competitive inhibition mechanism was attributed to the former. Results improved the understanding of the basic events of the impact of metals at biochemical levels in primary producers organisms.