A flow microcalorimetric method for enzyme activity measurements: Application to dihydrofolate reductase

✍ Scribed by Lucas Sica; Robert Gilli; Claudette Briand; Jean Claude Sari

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 597 KB
• Volume: 165
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(87)90279-x

✦ Synopsis

A flow microcalorimetric method was developed for the analysis of enzymatic activities in crude tissue homogenates. It can be applied whenever a heat exchange is involved in an enzymatic reaction. The consequent sensitivity obviously depends on the enthalpy variation observed. Dihydrofolate reductase was chosen as an example; this enzyme is the molecular target of methotrexate, a widely used anticancer agent. This calorimetric method, whose sensitivity limit is 1.48 X 10(-4) units of dihydrofolate reductase per milliliter of reactant medium, allows enzyme activity measurements in tissues with low dihydrofolate reductase levels. A few examples of measurements in animal tissues are given. These measurements are of some interest; indeed, increased activity and increased levels of this enzyme are two of the mechanisms which may explain resistance to methotrexate.