1.Kinetic studies of urokinase-catalysed hydrolysis of 5-oxo-L-prolylglycyl-L-arginine 4-nitroanilide.
Ipsen HH, Christensen U. Biochim Biophys Acta. 1980 Jun 13;613(2):476-81.
The enzymic properties of urokinase (EC 220.127.116.11) were studied. The kinetic parameters of hydrolysis of 5-oxo-Pro-Gly-Arg-NA were determined in the pH range 5-9, at 25 degrees C and 37 degrees C. The reaction is affected by only one ionizing group of urokinase with pK 7.15 (25 degrees C) and pK 6.82 (37 degrees C). The results indicate that 5-oxo-Pro-Gly-Arg-NA is a good model substrate for studies of the conversion of plasminogen to plasmin. The Km values of the urokinase-catalysed hydrolysis of plasminogen and 5-oxo-Pro-Gly-Arg-NA are of the same order of magnitude. Plasmin catalyses the hydrolysis of 5-oxo-Pro-Gly-Arg-NA, but the Km value is several hundred times that of urokinase. Urokinase is shown not to react with good plasmin substrates, such as Bz-Arg-OEt and D-Val-Leu-Lys-NA, but is linearly competitively inhibited by 6-amino-hexanoic acid and trans-4-aminomethylcyclohexane-1-carboxylic acid.
2.Primary specificity of alakaline mesentericopeptidase. Kinetic parameters for the hydrolysis of alpha-N-acetyl-L-amino acid methyl esters.
Stambolieva N, Chakarova R. Int J Pept Protein Res. 1978 Jan;11(1):37-41.
The steady-state kinetics of the alkaline mesentericopeptidase-catalysed hydrolysis of esters of the general formula Ac-X-OMe(OEt) has been studied, "X" being an amino acid residue (Ala, Val, Leu, Ile, Phe, Tyr, Trp, Lys). The values of the specificity ratio kcat/Km indicate that the bonds involving the carboxyl group of amino acids with aromatic and bulky aliphatic side chain are hydrolysed most effectively. On account of this, alkaline mesentericopeptidase is classified as a chymotrypisn-like alkaline protease. The primary specificity of mesentericopeptidase reveals the similarity of this enzyme to the group of subtilisins, as well as the distinctive characteristic feature of the enzyme to hydrolyse Ac-Leu-OMe with an efficiency practically equal to that of aromatic amino acid derivatives. Suggestions are made about the nature of the substrate-binding centre, taking into consideration Schechter's and Berger's concept of the secondary specificity.