About Us | Help Videos | Contact Us | Subscriptions

Journal of Environmental Quality Abstract -

Effects of Acidity and Alkalinity on the Stability of Amidohydrolases in Freshwater1


This article in JEQ

  1. Vol. 12 No. 4, p. 459-462

Request Permissions

  1. W. T. Frankenberger Jr. and
  2. A. L. Page2



The influence of acidity and alkalinity on the enzymatic hydrolysis of amide-N in the aquatic system was investigated by determining the stability of L-asparaginase (EC [Enzyme Commission] L-glutaminase (EC, and amidase (EC, and urease (EC with respect to pH in three freshwater lakes. The water samples were first incubated at the indicated buffer pH (1–13) for 24 h; then each enzyme was assayed at its optimal pH (pHopt) under standardized conditions. L-Asparaginase retained essentially 100% of its activity within the pH range of 6–7 in Lake Evans and Lake Matthews, and 5–7 in Lake Perris. L-Glutaminase was active between pH 6 and 7 in the water samples surveyed. Amidase remained completely active at pH ranges of 4–8 in Lake Evans, 4–7 in Lake Matthews, and 5–8 in Lake Perris. Urease remained active over a broad pH range of 5–9 in Lake Evans, 5–8 in Lake Matthews, and 4–8 in Lake Perris. There was a progressive loss in enzyme activity below and above these pH ranges. The results suggest that the decline in aquatic amidohydrolase activities in relation to the pH-profile near their pHopt was caused by a reversible reaction involving the ionization or deionization of functional groups of the active center of the protein, but under highly acidic or alkaline conditions (pH < 4 to > 9) the reduced activity appears to be due to irreversible inactivation of the enzyme.

  Please view the pdf by using the Full Text (PDF) link under 'View' to the left.

Copyright © .