|
type |
Journal Article |
authors |
Ramesh, K. S.; Appaji Rao, N. |
title |
Purification and physicochemical, kinetic and immunological properties of allosteric serine hydroxymethyltransferase from monkey liver |
journal |
Biochem J |
Activity |
2.1.2.1 |
ui |
84256487 |
year |
(1980) |
volume |
187 |
number |
3 |
pages |
623-36. |
| |
keywords |
Allosteric Regulation |
abstract |
The homogeneous serine hydroxymethyltransferase purified from monkey liver, by the use of Blue Sepharose affinity chromatography, exhibited positive homotropic co-operative interactions (h = 2.5) with tetrahydrofolate and heterotropic interactions with L-serine and nicotinamide nucleotides. The enzyme had an unusually high temperature optimum of 60 degrees C and was protected against thermal inactivation by L-serine. The allosteric effects were abolished when the monkey liver enzyme was purified by using a heat-denaturation step in the presence of L-serine, a procedure adopted by earlier workers for the purification of this enzyme from mammalian and bacterial sources. The enzyme activity was inhibited completely by N5-methyltetrahydrofolate, N5-formyltetrahydrofolate, dichloromethotrexate, aminopterin and D- cycloserine, whereas methotrexate and dihydrofolate were partial inhibitors. The insoluble monkey liver enzyme-antibody complex was catalytically active and failed to show positive homotropic co- operative interactions with tetrahydrofolate (h = 1) and heterotropic interactions with NAD+. The enzyme showed a higher heat-stability in a complex with its antibody than as the free enzyme. These results highlight the pitfalls in using a heat-denaturation step in the purification of allosteric enzymes. |
last changed |
2002/11/04 17:41 |
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