Biochemical and Kinetic Investigations of Partially Purified Thermostable Acid Phosphatases from Solanum tuberosum and Citrus limonium

Abstract

Biochemical and kinetic properties of partially purified thermostable acid phosphatases from Solanum tuberosum and Citrus limonium involving ammonium sulphate fractionation have been investigated. The maximum specific activity in Solanum tuberosum and Citrus limonium was found in 40–80% (ACP I) and
0–40% (ACP II) fractions, respectively. The specific activities of ACP I and ACP II were 46.01 and 48.00 units mg ^− 1 with K_m values of 1.00 and 2.50 mM, respectively. The phosphatases obtained from the two sources were thermally stable and displayed acidic activities by using para-nitrophenylphosphate as substrate. Values of temperature coefficients (Q10) and activation energy (E_a) were found to be 1.7, 1.5 and 44.7, 40.6 kJmol ^− 1 for ACP I and ACP II, respectively. ACP I activity was enhanced by Mg^2 +, Mn^2 +, Tween-20 and Cween-20. All the cations tested had slight inhibitory effect on ACP II. Sodium Lauryl Sulphate (SLS) acted as a strong inhibitor of both ACP I (uncompetitive) and ACP II, with inhibition constants (K_i) 4.6 × 10 ^− 4 and 5.5 × 10 ^− 4 M, respectively. ACP I was inhibited by most metals (except Mg^2 +, Mn^2 +) but the most powerful inhibitors were Cu^2 + (non-competitive) and Zn^2 + (non-competitive) with K_i values 2.2 × 10 ^− 4 and 1.0 × 10 ^− 5 M, respectively. These results suggest that the acid phosphatases (ACP I and ACP II) play an important role in energy transfer, releasing of inorganic phosphate and also due to thermostability might find potential applications in various bioindustries.