Cystathionase catalyses the formation of homocysteine from cystathionine; its formation in cultures of Escherichia coli is repressed by the presence of methionine in the growth medium, and to a similar extent to that shown with homocysteine methylase (the enzyme complex which catalyses the conversion homocysteine → methionine). Cystathionase, again like homocysteine methylase, is formed rapidly without concomitant growth when repressed organisms are transferred to a medium free from methionine; such enzyme formation is prevented by chloramphenicol, suggesting that de novo synthesis of protein is required. The co-repression by methionine of the two enzyme systems fortifies the evidence that cystathionase is a component of the normal pathway of methionine synthesis by E. coli and consequently that its substrate, cystathionine, is a normal intermediate. Cystathionase preparations also formed pyruvate from cysteine; this activity paralleled that of cystathionase itself when the methionine status of the medium was changed, and it is concluded that the same protein is responsible for both activities.
AmesB. N.,
GarryB.1959; Co-ordinate repression of the synthesis of four histidine biosynthetic enzymes by histidine.. Proc. nat. Acad. Sci., Wash. 45:1453
CohnM.,
CohenG. M.,
MonodJ.1953; L’effet inhibiteur spécifique de la méthionine dans la formation de la méthionine-synthase chez Escherichia coli.. C. R. Acad. Sci., Paris 236:746
GoriniL.,
MaasW. K.1958; Feedback control of the formation of biosynthetic enzymes. In The Chemical Basis of Development. Ed. by W. D. McElroy & B. Glass, p. 469. Baltimore: Johns Hopkins Press..
GuestJ. R.,
HelleinerC. W.,
CrossM. J.,
WoodsD. D.1960; Cobalamin and the synthesis of methionine by ultrasonic extracts of Escherichia coli.. Biochem. J. 76:396
GuestJ. R.,
WoodsD. D.1962; Metabolic interrelationships between cobalamin and folic acid in the synthesis of methionine by Escherichia coli. 2 Europaisches Symposion iiber Vitamin B12und Intrinsic Factor. Ed. by H. C. Heinrich, p. 686. Stuttgart : Ferdinand Enke Yerlag..
LampenJ. O.,
RoepkeR. R.,
JonesM. J.1947; Studies on the sulfur metabolism of Escherichia coli. III. Mutant strains of Escherichia coli unable to utilize sulfate for their complete sulfur requirements.. Arch. Biochem. 13:55
LayneE.1957; Spectrophotometric and turbidimetric methods for measuring proteins. In Methods in Enzymology. Ed. by S. P. Colowick & N. O. Kaplan. New Academic Press. 3:451
VogelH. J.1957; Repression and induction as control mechanisms of enzyme biogenesis: the ‘adaptive’ formation of acetylornithinase. In The Chemical Basis of Heredity. Ed. by W. D. McElroy & B. Glass. Baltimore: Johns Hopkins Press. 276:276
WijesunderaS.,
WoodsD. D.1953; The effect of growth on a medium containing methionine on the synthesis of this amino acid by Bacterium coli.. Biochem. J. 55:viii
WijesunderaS.,
WoodsD. D.1960; Suppression of methionine synthesis in Escherichia coli by growth in the presence of this amino acid.. J. gen. Microbiol. 22:229