Purification and Properties of 5-Methyltetrahydropteroyltriglutamate-Homocysteine Transmethylase
Year: 1970
Type: article
Abstract: 5-Methyltetrahydropteroyltriglutamate-homocysteine transmethylase has been purified from a methionine auxotroph of Escherichia coli K12, which was derepressed for the enzyme.The purified transmethylase has been crystallized and appears to be nearly homogeneous by disc gel electrophoresis and by equilibrium and velocity ultracentrifugation.Further evidence for a high degree of purity has been obtained from a dual purification of the enzyme from repressed and derepressed cells.A calculation of the specific activity of pure enzyme from the initial and final specific activities of derepressed and repressed enzymes reveals that the purified derepressed enzyme is at least 94% pure.Since the transmethylase appears nearly homogeneous after only a ZO-fold purification, the enzyme must represent 5% of the soluble protein in derepressed cells of E. coti and 3% in wild type cells.The catalytic, physical, and chemical properties of the purified transmethylase have been investigated.The formation of methylJ4C-methionine from 5-methyl-W-tetrahydropteroyltriglutamate is dependent on transmethylase, homocysteine, and Pi and is stimulated by Mg+2.5-Methyl-W-tetrahydropteroylglutamate or 5-methylJ4C-tetrahydropteroyl-a!-glutamylglutamate cannot replace the triglutamate folate derivative as methyl donor in the formation of methionine.The formation of methionine is inhibited by high ionic strength, ethylenediamine tetraacetic acid, and the folate substrate analogues pteroyl-cr-glutamylglutamic acid, pteroyl-y-glutamyl-y-glutamylglutamic acid, and 5-methyltetrahydropteroyl-a!-glutamylglutamate,The transmethylase has a molecular weight of 84,000 and appears to be composed of subunits.
Source: Journal of Biological Chemistry
Language: English
Subfield: Rheumatology
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1533310140