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Influence of ammonium salts on the lipase/esterase activity assay using p ‐nitrophenyl esters as substrates
Author(s) -
Yan Hong,
Zhang Yin Jun,
Liu Hong Cai,
Zheng Jian Yong,
Wang Zhao
Publication year - 2013
Publication title -
biotechnology and applied biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.468
H-Index - 70
eISSN - 1470-8744
pISSN - 0885-4513
DOI - 10.1002/bab.1095
Subject(s) - chemistry , lipase , hydrolysis , esterase , ammonium , ammonium sulfate precipitation , ammonium sulfate , sulfate , chromatography , enzyme , organic chemistry , size exclusion chromatography
p ‐ N itrophenyl esters with a short‐chain carboxylic group, such as p ‐nitrophenyl acetate ( p ‐ NPA ) and p ‐nitrophenyl butyrate ( p ‐ NPB ), could be effectively hydrolyzed by ammonium salts. p ‐ N itrophenyl esters were usually used as substrates to assay the lipase/esterase activity. Ammonium sulfate precipitation was often used to purify proteins, and some ammonium salts were usually used as nitrogen sources or inorganic salts for the lipase/esterase production. To study the effect of ammonium salts on the assay of the lipase/esterase activity, the contributing factors of hydrolysis of p ‐ NPA / p ‐ NPB catalyzed by ammonium salts were investigated. The lipase activities were compared in the presence and absence of ammonium sulfate. The hydrolysis reaction could be catalyzed under neutral and alkaline circumstances. The hydrolysis rate increased with the increase in the reaction temperature or the concentration of ammonium ion. When p ‐ NPA was employed as the substrate for the analysis of the lipase/esterase activity, the effect of ammonium sulfate on the analysis could be neutralized by setting a control when the concentration of ammonium sulfate was less than 40% saturation. However, when the concentration of ammonium sulfate increased from 40% to 100% saturation, the enzyme activities decreased about 13–40%, which could not be ignored for accurate analysis of the enzyme activity.