title: Rat kidney histamine N-methyltransferase: purification and partial characterization.
abstract: Histamine N-methyltransferase (HMT, EC 2.1.1.8) was purified 8,420-fold in 44% yield from rat kidney. The basic steps in the purification included differential centrifugation, calcium phosphate adsorption, DEAE cellulose chromatography, and affinity chromatography on an S-adenosylhomocysteine-agarose matrix. The resulting protein was homogeneous as determined by gel electrophoresis and was stable for at least five months at -80 degrees C. The apparent molecular weight of the enzyme was found to be 31,500 as determined by gel filtration through Sephadex G-100 and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point of the enzyme was determined to be 5.4. The Km's for histamine and S-adenosyl-L-methionine were 12.4 +/- 1.3 microM and 10.2 +/- 0.5 microM, respectively. When S-adenosyl-L-methionine was the variable substrate, the Ki's for S-adenosyl-L-homocysteine and S-adenosyl-D-homocysteine were 31.9 +/- 3.4 microM and 32.0 +/- 3.5 microM, respectively. When histamine was the variable substrate, the Ki for S-adenosyl-L-homocysteine was 11.8 +/- 0.6 microM. Comparison of physico-chemical and catalytic properties of the rat kidney and the guinea pig enzymes suggest that these proteins have similar structural and catalytic characteristics.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001921:Brain / Q000201:enzymology; D002850:Chromatography, Gel; D006637:Histamine N-Methyltransferase / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D008780:Methyltransferases / Q000302:isolation & purification*; D008970:Molecular Weight; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000596:Amino Acids; D008780:Methyltransferases; D006637:Histamine N-Methyltransferase