A simple assay for methionine adenosyltransferase using cation exchange paper and liquid scintillation spectrometry

✍ Scribed by R.M. McKenzie; R.K. Gholson

• Book ID: 102983139
• Publisher: Elsevier Science
• Year: 1973
• Tongue: English
• Weight: 547 KB
• Volume: 53
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(73)90084-5

✦ Synopsis

A rapid, sensitive and simple procedure for the assay of L-methionine-~-adeno~ltr~nsferase based on the use of phosphocellulo~ ion-exchange paper is presented. The analytical procedure may be generally useful for all enzymes where there is a large cationic charge difference between the substrates and products. An application of a simplified counting procedure for radioisotopes on solid supports is presented.

This work was promp~d by the need for a rapid dependable assay for methionine adenosyltransferase (EC 2.4.2.13) which would be useful for comparative biochemical studies in crude liver homogenates. There are several published assays for this enzyme (l-5) based on spectrophotometric or radioisotopic methods. However, none of them proved satisfactory for our purpose. The spectrophotometric assays (l&4) are not sensitive enough to use with small amounts of crude extracts. The published assays based on radioisotopes were carried out on purified enzyme and using less than Km levels of substrate. These low substrate levels result in large underestimation of activities. Biochemical assays for several kinases and phosphoribosyltransferases using DEAE cellulose ion exchange papers have been developed during recent years (G-10). These assays, in general are rapid and sensitive. This type of analysis is feasible if any limitations imposed by the ion exchange capacity and selectivity of the ion exchange paper can be overcome. Newsholme et al. (7) suggested that carboxymethylcellulose and *Journal Article J2521 of the Agricultural Experiment Station,