No abstract

TONG, J. H., PE~TCLERC, C., D'IORIO, A., and BENOITON, N. L. Resolution of ring-substituted phenylalanines by the action of a-chymotrypsin on their ethyl esters. Can. J. Blochem. 49, 877-881 (1971).The D-and L-isomers of the following ring-su bsti tu ted phenylalanines have k e n prepared from the racemates in $8-$0% yield: tyrosine, o-tyrosine, m-tyrosine, p-chlorophenylalanine, p-Wuorophenylalanine, and 3,4-dihydroxyphenylalanine. The resolutions were effected by digestion of the racemic ethyl esters with a-chymotrypsin at pH 5.0 (pH-stat). The L-isomers were crystallized from the concentrated digests; the D-isomers were obtained by saponification of the remaining D-esters after extraction into ethyl acetate. Analysis of the isomers by column chromatography indicated optical purities greater than 99.5%. The racemic esters were prepared with ethanol / hydrogen chloride and were used without isolation. TONG, J. H., PETITCLERC, C., D'IORPO, A., et BENOHTON, N. L. Resolution of ring-substituted phenylalanines by the action of a-chymotrypsin on their ethyl esters. Can. J. Biochem. 49,877-881 (1971). Du mtlange radmique, nous avons prkpart, avec des rendements variant de 60% & 80%, les isomeres D et L des phknylalanines suivantes substituQs dans le noyau: tyrosine, o-tyrosine, m-tyrosine, p-chlorophknylalanine, p-fluorophknylalanine, et 3,4-dihydroxyphknylalanine. Les rtsolutions sont effectuks par digestion des esters Cthyliques ractmiques avec I'a-chymotrypsine a pH 5.0 (pH-stat). Les L-isom&res sont cristallisks A partir des produits concentrb de la digestion les D-isom&res sont obtenus par saponification des D-esters qui restent apres extraction dam l'adtate d'tthyle. L'analyse des isomkres par chrsmatographie sur colonne indique des puretts optiques plus grandes que 99.5%. Nous avons prtpart les esters rackmiques avec I'tthanol / chlorure d'hydrogene et nous les avons utilkts sans isolation.A recent study by us of the metabolism of the optical isomers of o-hydroxyphenylalaninae (o-tyrosine) required the resolution of the "Clabelled racemate (1). This was accomplished by use of the stereospecific hydrolytic action of a-chyrnotrypsin on the racemic amino acid ester at pH 5 (2). The simplicity and other attractive features of this method have prompted us to apply it to the resolution of other ring-substituted phenylalanines. This paper describes the results of these experiments. A kinetic study of the interaction of a-chymotrypsin with carboxyl-substituted phenylalanines has already been published (3). ExprfmewtalMaterials DL-@-Tyrosine and 3,4-dihydroxy-DL-phenylalaniloe (DL-Dopa) were purchased from Mann Research Laboratories, Orangeburg, N.Y.; DL-m-tyrosine, from Moch-

Particulate catechol-O-methyltransferase (COMT) from rat liver has been solubilized by acetone treatment and partially purified. Results from the present study demonstrate that the solubilized, partially purified enzyme is similar to the cytosol COMT with respect to molecular weight, pH profile, sensitivity toward inhibitors, Mg2+ requirement, and substrate affinities. However, a comparison of the crude particulate COMT and the solubilized enzyme shows that there is a significant difference in their affinity for catechol substrates. This finding suggests that membrane protein and (or) lipid components may play an important role in catecholamine metabolism. The relationship of particulate COMT to [3H]norepinephrine binding was investigated. No correlation between the COMT and [3H]norepinephrine binding activities was observed in vitro.

The solubilized monoamine oxidase activity of rat liver, kidney, and brain can be separated into several bands by cellulose polyacetate membrane electrophoresis. Four such bands of activity are found in the whole liver homogenate while mitochondrial and microsomal fractions appear to have two. The activity of these bands has been assayed using three different substrates, isoamylamine, tyramine, and benzylamine. The solubilized mitochondrial monoamine oxidase activity of kidney and brain when submitted to electrophoresis is found to separate in two fractions. There is some small but consistent difference of distribution of activity when using different substrates.

The substrate specificity of mitochondrial monoamine oxidase (MAO) in pancreatic and adipose tissues of obese mice and their lean counterparts was determined. The pancreatic MAO of obese mice had a greater specific activity than that of the lean mice. The white adipose tissue MAO was found to be more active than the brown adipose MAO in both groups of mice. While there was no appreciable difference in the MAO activities of brown adipose tissues between obese and lean mice, the enzyme from the white adipose tissue of obese mice had a higher specific activity than that of the lean mice. The higher MAO activity in white adipose tissue was observed when tyramine or serotonin was employed as substrate but not with benzylamine. Examination of mitochondrial MAO from epididymal adipocytes revealed marked differences in the properties of the enzyme between whole adipose tissue and isolated adipocytes. The inhibition characteristics of MAO from these tissues were studied with the specific inhibitors clorgyline and deprenyl.