Kinetics and inhibition by some aminoacids of lactating rat mammary gland arginase.
Some kinetic and regulatory properties of lactating rat mammary gland arginase were studied. At pH 7.4, i.e. at near-physiological conditions, there was evidence of inhibition by excess of substrate, with a Km value of 9.5 mM, slightly lower than the value of 18 mM observed at pH 9.8 (maximum enzyme activity). A study was also made of the effects of proline, ornithine, lysine and certain branched-chain aminoacids on enzyme activity: lactating rat mammary gland arginase was strongly and competitively inhibited by lysine, ornithine and valine, with Ki values of 1.2 mM, 1.1 mM and 3.6 mM, respectively. Other aminoacids (proline, isoleucine and leucine) also inhibited lactating rat mammary gland arginase, although to a lesser extent.
Departamento de Bioquímica, Facultad de Veterinaria, Universidad de Extremadura, Cáceres, Spain.
J M
JM
Fuentes
M L
ML
Campo
G
G
Soler
D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D001119:Arginase / Q000187:drug effects*; D005260:Female; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000187:drug effects* / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar
D000596:Amino Acids; D001119:Arginase