Deoxyribose Phosphate Aldolase from Rat Liver.

The activity and properties of deoxyribose phosphate aldolase from Escherichia coli and Lactobacillus plantarum have been described in detail by Racker (1) and Pricer and Horecker (2). The enzyme from E. coli was shown to be active at pH values between 6.0 and 8.0 in tris(hydroxymethyl)aminomethane and phosphate buffers without exhibiting a sharp optimum (1). The enzyme from L. plunturum was shown to have a maximal reaction velocity at pH 6.3 when a combination of several buffers were used to cover the pH range from 4.0 to 10.0. In addition this enzyme was reported to require a carboxylic acid for full activity (2). Boxer and Shonk (3) reported interesting differences in the intracellular distribution of the enzyme between normal liver tissue, regenerating liver, and malignant tissue. Their data indicate that in normal liver the synthetic capacity is found primarily in the nuclear fraction (precipitated at 600 X g), ‘whereas the disappearance of deoxyribose phosphate occurs in the supernatant fraction after removal of the cellular pa.rticulates. An enzyme preparation obtained by precipitation at 40 To saturation with ammonium sulfate catalyzed the formation of deoxyribose-5-P but the reversibility of the enzymatic action could not be demonstrated. A fraction precipitating between 40 and 60% saturation was reported to catalyze the disappearance of deoxyribose-5-P but the products of this reaction could not be identified. The cleavage of deoxyribose-5-P by an enzyme preparation from rat liver to form acetaldehyde and glyceraldehyde-3-P and the requirement of this preparation for a carboxylic acid for maximal activity have recently been reported by Jiang and Groth (4). Preliminary investigations in this laboratory indicated that deoxyribose phosphate aldolase was present almost exclusively in the soluble supernatant fraction of rat liver homogenates and its activity and pH optimum were considerably influenced by the type of buffer used in the enzymatic assay. This paper describes the purification and properties of the enzyme from the soluble supernatant fraction of rat liver. The experimental data show tha.t this enzyme catalyzes the formation of deoxyribose-5-P and the reversible cleava.ge of deoxyribose-5-P to acetaldehyde and glyceraldehyde-3-P and has other properties similar to the bacterial enzyme described by Pricer and Horecker (2).