Properties of rat liver L-threonine deaminase.
We have studied several properties of rat liver L-threonine deaminase: (1) the affinity for the two substrates, L-serine and L-threonine; (2) the threonine/serine activity ratio which changes with increasing pH; (3) the activation, by pyridoxal 5'-phosphate which is linked to the nonprotonated form of the coenzyme and to at least an -SH group of the enzyme, and (4) the reactivation by pyridoxal 5'-phosphate and pyridoxamine 5'-phosphate after dissociation of the coenzyme. The mechanism of the reactivation by pyridoxamine 5'-phosphate is the most interesting problem opened by the present research.
Pagani
R
R
Institute of Biochemistry and Enzymology, University of Siena, Italy.
Leoncini
R
R
Pizzichini
M
M
Vannoni
D
D
Tabucchi
A
A
Marinello
E
E
D000818:Animals; D001051:Apoenzymes / Q000378:metabolism; D002850:Chromatography, Gel; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D011732:Pyridoxal Phosphate / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000378:metabolism; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism; D013913:Threonine Dehydratase / Q000302:isolation & purification / Q000378:metabolism*
D001051:Apoenzymes; D013912:Threonine; D012694:Serine; D011732:Pyridoxal Phosphate; D013913:Threonine Dehydratase