Physico-chemical properties of thymidylate synthase from Lactobacillus leichmannii: thiol groups, amino acid composition and the terminal end-groups.
Thymidylate synthase (5,10-methylenetetrahydrofolate: deoxyuridylate C-methyltransferase, EC 2.1.1.45) from Lactobacillus leichmannii was completely inactivated after 5 min of heat treatment at 55 degrees C. A remarkable synergistic effect with no loss in activity was noted when 10(-3) M dUMP was added to the enzyme before subjecting to heat treatment. The enzyme got activated in the presence of 2-mercaptoethanol (75 mM) and inhibited by pCMB (I50 = 5 microM). It had 2 free sulfhydryl groups and a single disulfide bond. The two identical subunits of the 74 kDa dimer were possibly bonded by a single disulfide linkage. It had a total of 652 amino acids with methionine as the amino-terminal and alanine as the carboxy-terminal amino acid residues. The carboxy-terminal end-group alanine was preceded by valine, lysine and proline sequentially in that order.
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Radiation Biology and Biochemistry Division, Bhabha Atomic Research Centre, Bombay, India.
D000596:Amino Acids / Q000032:analysis; D004789:Enzyme Activation; D004795:Enzyme Stability; D007700:Kinetics; D007778:Lactobacillus / Q000201:enzymology*; D008623:Mercaptoethanol / Q000494:pharmacology; D008970:Molecular Weight; D011489:Protein Denaturation; D013438:Sulfhydryl Compounds / Q000032:analysis; D013816:Thermodynamics; D013940:Thymidylate Synthase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism
D000596:Amino Acids; D013438:Sulfhydryl Compounds; D008623:Mercaptoethanol; D013940:Thymidylate Synthase