Studies on kinetic properties of acid phosphatase from nuclei-free rat liver homogenate using different substrates

Abstract

<span style="font-size:14.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:hi"="" lang="EN-IN">Kinetic properties of rat liver acid phosphatase were evaluated using the conventional synthetic substrates sodium beta glycerophosphate (βGP) and <i>p</i>-nitrophenyl phosphate (PNPP) and physiologically occurring phosphate esters of carbohydrates,vitamins and nucleotides. The extent of hydrolysis varied depending on the substrates; phosphate esters of vitamins and carbohydrates were in general poor substrates. Kinetic analysis revealed the presence of two components of the enzyme for all the substrates. Component I had low K_m and low V_max. Opposite was true for component II. The K_m values were generally high for βGP, PNPP and adenosine diphosphate (ADP). Amongst the nucleotides substrates AMP showed high affinity i.e. low K_m. The increase in enzyme activity in general at high substrate concentrati on seems to be due to substrate binding and positive cooperativity. AMP which showed highest affinity was inhibitory at high concentration beyond 1m<i>M</i>. The results suggest that in <i>situ</i> the nucleotides may be the preferred substrates for acid phosphatase.</span>