Quantitative turbidity assay for lipolytic enzymes in microtiter plates

Anal Bioanal Chem. 2013 Oct;405(26):8539-47. doi: 10.1007/s00216-013-7283-5. Epub 2013 Aug 29.

Abstract

A clearing assay for lipolytic enzymes has been realized in 96-well microtiter plates. A thin layer containing emulsified tributyrin as turbidity-generating substrate was placed on a thicker supporting aqueous layer. Both layers were stabilized by a gel-forming agent. Enzyme addition leads to clearing of the emulsion detected with a standard microtiter plate reader as a decrease of extinction. Dependencies of the signal kinetics on the substrate and enzyme concentrations were studied. For 0.5-1% tributyrin content the reaction rate is not substrate-limited. An initial slope of the signal kinetics is proportional to the lipase activity. A detailed characterization of the assay was performed. Lipolysis of tributyrin was confirmed by glycerol detection. Various gel-forming agents were compared and diffusion conditions in these gels were analyzed. Agar and agarose were found to be the most suitable gel-forming agents, which do not affect enzyme diffusion whereas polyacrylamide gels block lipase diffusion and therefore are not suitable for the assay. The optimized assay prepared from 1% tributyrin emulsion in 2% agar gel was tested with six microbial lipases and porcine pancreatic lipase. The detection limit is 20-60 ng/well which is equivalent to 30 μU/well for T. lanuginosus lipase.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacteria / enzymology
  • Emulsions / chemistry
  • Emulsions / metabolism*
  • Enzyme Assays / methods*
  • Fungi / enzymology
  • Kinetics
  • Limit of Detection
  • Lipase / analysis
  • Lipase / metabolism*
  • Substrate Specificity
  • Swine
  • Triglycerides / chemistry
  • Triglycerides / metabolism*

Substances

  • Emulsions
  • Triglycerides
  • Lipase
  • tributyrin