Purification and properties of choline kinase from rat brain.
Biochim Biophys Acta
; 1043(3): 281-8, 1990 Apr 17.
Article
em En
| MEDLINE
| ID: mdl-2157491
ABSTRACT
A blue-dye column separated rat brain choline kinase (EC 2.7.1.32) into two peaks, very likely corresponding to distinct isozymes. The major-peak enzyme was purified 15,000-fold to homogeneity. The final specific activity was approx. 40 mumol.min-1.mg-1. This is 10-times higher than that reported for the enzymes from lung and kidney. The purified enzyme gave a single 44 kDa protein band on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Analytical gel-filtration showed that the native enzyme had a molecular weight of 90,000 and a Stokes radius of 4.2 nm. The sedimentation coefficient was deduced to be 4.8 S and the molecular weight 87,600 by sucrose-density-gradient centrifugation. Hence, the native enzyme appears to be a dimer. The apparent Km values for ATP and choline were 1.0 mM and 14 microM, respectively. At high choline concentrations, the enzyme showed deviation from Michaelis-Menten kinetics. The enzyme was active in a high pH range and utilized a variety of amino alcohols structurally related to choline, including ethanolamine, N-methylethanolamine and N,N-dimethylethanolamine as substrates. Spermine and spermidine stimulated the enzyme by decreasing the apparent Km for ATP and increasing Vmax. Although less efficiently, monovalent cations such as NH4+, K+, Li+ and Na+ and quaternary amines such as carpronium, chlorocholine and acetylcholine were also stimulatory.
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Base de dados:
MEDLINE
Assunto principal:
Fosfotransferases
/
Encéfalo
/
Colina Quinase
Limite:
Animals
Idioma:
En
Revista:
Biochim Biophys Acta
Ano de publicação:
1990
Tipo de documento:
Article
País de afiliação:
Japão