Vol. 10, Issue 7 (2021)

Author(s):
Dr. J Aruna Kumari and Dr. A Padmasri

Abstract:
Substrate concentration of enzyme is one of the factor which effect the enzymes kinetics, to study the role of substrate concentration on soil enzyme Acid phosphatase in selected soils. Forty soil samples were collected and assayed for the activity of soil acid phosphatase and four soil samples, two Alfisols and two Vertisols soils with high activity were selected for further study. The activity of acid phosphatase as expressed in terms of µg of 4-nitrophenol released g^-1 soil h^-1 ranged from 18.93 to 51.2 with an average value of 31.79 activities of the surface soils Soil acid phosphatase increased with increase in substrate concentration upto 30mM and almost reached a plateau at a substrate concentration of more than 30mM at higher concentrations the enzyme activity remained almost constant in all the four soils. With further increase in substrate concentration, minimal change in enzyme activity was observed. Characteristics of enzyme activities like maximum enzyme reaction velocity (V_max) and Michaelis constant (K_m) were determined using Michaelis – Menten equation similar to those determined in homogenous system. The maximum reaction velocity of soil acid phosphatase for soils under study were calculated (µg of 4-nitrophenol g^-1 soil h^-1) and varied from 40.0 to 56.6 and followed the sequence VS I >AS II > AS I >VS II using Lineweaver – Burk plot. The values compared well with Hanes – Wolf transformation 46.0 to 56.0 and followed the sequence VS I >VSII > AS II >AS I under and Eadie – Hofstee transformation the values varied from 44.0 to 54.4 and followed the order VS I >VS II >AS II >ASI. Michaelis constant (K_m) of the soil acid phosphatase calculated using Lineweaver – Burk transformation plot varied from 0.44mM to 0.60mM and followed the order is VS I >AS II >AS I >VS II. The values compared well with those obtained from Hanes – Wolf (0.63 to 0.86) and followed the order is VS II >ASI >VS I >AS II. In Eadie – Hofstee plots the values ranged from (0.51 to 0.65) and the order followed is VS I >AS II >AS I >VS II.