The kinetics of hydrolysis of derivatives of arginine, homoarginine and ornithine by trypsin.

Trypsin catalyses the hydrolysis of suitable derivatives of basic amino acids including peptides, amides and esters. Esters are the most sensitive substrates, and it was decided to use them in the present study, which had as one of its aims the elucidation of the relationship between the length of the side chain and susceptibility to hydrolysis by trypsin. Previous investigations had shown that poly-L-ornithine and diand tri-ornithine (Brand, Plentl & Erlanger, 1949; Erlanger, 1957) are resistant to trypsin, although a-N-benzoyl-Lornithine amide is a substrate (Izumiya, Okazaki, Matsumoto & Takiguchi, 1959). The ethyl ester of a-N-benzoyl-DL-homoarginine (Kitagawa & Izumiya, 1959), but not the corresponding L-amide (Shields, Hill & Smith, 1959), is hydrolysed by trypsin. We decided to examine members of two series of compounds, namely (I) and (II), as potential substrates; cx-N-toluene-p-sulphonylderivatives were chosen, since ac-N-toluene-p-sulphonylL-arginine methyl ester is a particularly sensitive substrate for trypsin. In the present paper, the kinetics of the trypsin-catalysed hydrolysis of several esters of oc-N-toluene-p-sulphonyl-L-arginine and -L-homoarginine, and of the methyl ester of ac-N-toluene-p-sulphonyl-L-ornithine, are described. A preliminary account of some of this work has appeared (Elmore & Baines, 1960).