A single column method for the assay of adenylate cyclase

An improved, one-step method for the separation of cyclic AMP from other nucleotides on disposable columns of neutral aluminum oxide is described. The method consists of several modifications of an established assay for adenylate cyclase. These modifications were designed to increase the sensitivity of the method, to decrease the time required for column preparation, and to eliminate the variable elution patterns for cyclic AMP that are obtained when using aluminum oxide from different commercial sources. Uniform elution patterns and high recoveries (approximately 80%) of cyclic AMP were obtained when 0.1 M ammonium acetate was used to elute cyclic AMP instead of Tris-HCl buffer. Prior to column chromatography, the adenylate cyclase reactions were terminated with the addition of hydrochloric acid and the mixtures were heated to degrade acid-labile nucleotides that would otherwise elute with cyclic AMP from aluminum oxide columns. Disposable polypropylene columns, fabricated with a reservoir and fast-flow filters, were used for column chromatography. Low blank values, generally less than 15 dpm/assay tube, were obtained when the acidified reaction mixtures were applied directly to aluminum oxide columns without prior neutralization. The proposed method should be useful for the routine assay of adenylate cyclase activity.