Abstract
A new assay procedure for measurement of rat liver mitochondrial choline dehydrogenease was developed. Oxidation of [ methyl- 14C]choline to [ methyl- 14C]betaine aldehyde and [ methyl- 14C]betaine was measured after isolating these compounds using HPLC. We observed that NAD + was required for conversion of betaine aldehyde to betaine in rat liver mitochondria. In the absence of this cofactor, oxidation of choline led to the accumulation to betaine aldehyde. The apparent K m of the mitochondrial choline dehydrogenase for choline was 0.14–0.27 mM, which is significantly lower than previously reported. A partially purified preparation of choline dehydrogenase catalyzed betaine aldehyde formation only in the presence of exogenous electron acceptors (e.g., phenazine methosulfate). This preparation failed to catalyze the formation of betaine even in the presence of NAD +, indicating that betaine aldehyde dehydrogenase may be a separate enzyme from choline dehydrogenase.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - General Subjects
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