Lead toxicity and biochemical characterization of delta-ALAD on endemic prawn, Palaemonetes turcorum

Abstract

The aim of this studuy was to determine the toxic effect of lead (Pb) on Palaemonetes turcorum, which is endemic to Turkey, in vivo and its inhibitory effect on its delta-Aminolevulinic acid dehydratase (ALAD; E.C.4.2.1.24) in vitro, and characterize the enzyme's biochemical features. The LC50 (96 h) value, due to Pb toxicity and its confidence limits in vivo, were calculated by the EPA Probit Analysis Program. The inhibition effect of Pb on Palaemonetes turcorum's ALAD was determined in vitro. The enzyme was partially purified with ammonium sulfate and a Sephadex G-200 gel medium. The LC50 value for Pb was found to be 21.98 ppm in Palaemonetes turcorum. It was also observed that the inhibition of the enzyme and the amount of Pb in the liver (hepatopancreas) had increased. It was found that the optimum pH of Palaemonetes turcorum ALAD was about 7.0 and the enzyme was resistant to heat up to 55 degrees C. As a result of kinetic analyses, the V-max value and K-m value were found to be 22.83 nmol phorphobilinogen (PBG)/h/mg protein and 0.06 mmol/reaction mixtures, respectively. The enzyme was purified 51 fold with ammonium sulfate and a Sephadex G-200 gel medium, consecutively. As a result of the study held with SDS-PAGE, the enzyme's molecular mass was about 237.6 kDa.