Biochemical Investigations of Thermostable Acid Phosphatases from Pisum sativum and Triticum aestivum Cotyledons

Abstract

Biochemical Investigations were carried out to ascertain some properties of acid phosphatases (ACPs) extracted from Pisum sativum and Triticum aestivum cotyledons named as ACP I and ACP II, respectively. The phosphatases obtained from the two sources were thermally stable (up to 700C) and displayed acidic activities by using para-nitrophenyl phosphate as substrate. The specific activities of ACP I and ACP II were 81.9 and 42.6 unitsmg-1 with Km values of 2.85 and 2.50 mM, respectively. Values of temperature coefficients (Q10) and activation energy (Ea) were found to be 1.7, 1.5 and 44.7, 40.6 kJmol-1 for ACP I and ACP II, respectively. ACP II activity was enhanced by Mg2+, Mn2+, Tween-20 and Cween-20. All the cations tested had slight inhibitory effect on ACP I. Sodium Lauryl Sulphate (SLS) acted as strong inhibitor of both; ACP I and ACP II, with inhibition constants (Ki) 4.6 x 10-4 and 5.5 x 10-4 M, respectively. ACP II was inhibited by most metals (except Mg2+, Mn2+) but the most powerful inhibitors were Cu2+ (uncompetitive) and Fe2+ (non-competitive) with Ki values 8.7 x 10-5 and 2.5 x 10-5 M, respectively. These results suggest that the acid phosphatases (ACP I and ACP II) play an important role in energy transfer; release of inorganic phosphate and also due to thermostability might act as potential biocatalysts for bio-industrial applications