Extractability and intracellular localisation of urea cycle enzymes from rat liver.

1. Urea cycle enzymes and ornithine ketoacid transaminase were extracted from rat liver using various buffer systems and different procedures for the mechanical disintegration of the cells. Of the buffers tested, phosphate and glutathipne gave optimal results, whereas significant differences were found when other extracting media were used: activities of ornithine ketoacid transaminase and ornithine carbamyl transferase were significantly decreased in triethanolamineand in tris-[hydroxymethyl]-amiiiomethane (tris)-buffer when compared with phosphate. Arginase activity remains unchanged in phosphate and in tris-buffer, but it decreased significantly in triethanolamine-buffer. With the exception of ornithine ketoacid transaminase, no significant increase of enzyme activities were found when livers were extracted with 0.1 % cetylammonium bromide and distilled water respectively.