Abstract
Abstract An acetone powder of cat brain catalyzed the synthesis of two radioactive products when incubated with l-aspartate-14C and acetyl coenzyme A. The products were identified as N-acetyl-aspartic acid and citric acid. A water extract of the powder contained the system that produced citrate-14C, while the residue contained the aspartate N-acetyltransferase activity. The soluble system rather than the residue exhibited characteristics previously reported for a soluble aspartate N-acetyltransferase preparation of rat brain; hence, it is suggested that previous investigators were not measuring true l-aspartate N-acetyltransferase activity.
Highlights
This paper describes an enzyme preparation from the brain of rats that unequivocally synthcsizcs N-acetyl-L-aspartic acid from
Preliminary experiments with a rat brain acetone powder indicate that it gives the same results as reported here for the cat brain powder
Goldstein’s homogenization procedure solublizes a portion of the enzyme act.ivity. He could have been working with the soluble system reported here that makes citrate
Summary
1. Preparation of Enzymes-The cerebrum from an adult cat was removed after the cat was killed by cervical spine compression and immediately placed in 9 volumes of an acetone-Dry Ice mixture. The remainder of the procedure was conducted in a cold room at 4”. The tissue was homogenized with a Waring. The cont,ents were transferred to a graduated cylinder, and, after standing for 10 min, the supernatant was aspirated. The sediment was washed twice with the previous volume of the acetone-Dry Ice mixture, lyophilized, and stored in a desiccator at 4”. Aliquots of the powder were used for measurement of the enzyme activity
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