Paper Chromatographic examination was made of the products of the reaction of radioactive serine with homocysteine in the presence of crude rat or human liver homogenates. Much radioactive cysteine was formed as well as radioactive cystathionine. It was shown that the cystathionine produced in the reaction was partially further converted to cysteine by cystathionase. The amount converted increased with the concentration of enzyme and of pyridoxal phosphate used, and varied according to the tissue and species from which the enzyme extract was prepared. A modified assay for cystathionine synthase is proposed, in which the 14C transferred from l-[3-14C] serine to cystathionine is measured as the total radioactivity of both the cystathionine and cysteine produced. These substances are separated from serine on paper chromatograms of the trichloroacetic acid-soluble fraction of the reaction mixture, and eluted for counting. This method was tested using crude rat liver homogenates, and was then used to determine the cystathionine synthase activity of some human tissues.
All Science Journal Classification (ASJC) codes
- Clinical Biochemistry
- Biochemistry, medical