Folic acid and the synthesis of methionine by extracts of Escherichia coli

Abstract

566K. SELBY 1961 3. These comparisons suggest that the enzyme, being composed of large molecules with restricted mobility in the substrate, removes a number of adjacent glucose residues from each of relatively few sites of attack.A portion of this research was conducted under a project authorized by U.S. Public Law no. 480, 83rd Congress.

Two enzymic mechanisms for the methylation of homocysteine by extracts of Escherichia coli

“…E. coli strains 121/176 and 113/3 were both auxotrophs requiring methionine or cobalamin for growth, and were derived from the prototrophic strain W (Davis & Mingioli, 1950 Organisms weregrown on solid defined media in enamelled trays as described by (1960) modified by the use of 20 mM-potassium phosphate buffer, pH 7-8, containing 2-mercaptoethanol (7 mM) both for the preparation of suspensions of organisms before ultrasonic treatment and for the dialysis of the extracts. Extracts of acetone-dried organisms (strain PA15) were prepared as described by Jones et al (1961).…”

“…was prepared according to the method of Jones et al (1961) from pteroyl-y-glutamyl-y-glutamylglutamic acid (PtG,) …”

“…A cofactor of the folic acid group* is essential, and with E. coli PA 15 an extract of the heated organisms, H4PtG3 and its N5-and N'0-formyl derivatives are all effective. H4PtG inhibits competitively the action of both H4PtG3 and the extract of heated E. coli (Szulmajster & Woods, 1960;Jones, Guest & Woods, 1961); such inhibition does not, however, occur if cobalamin is added either to the ultrasonic extracts or to the medium on which the organisms are grown (Kisliuk & Woods, 1960; Guest, Helleiner, Cross & Woods, 1960). With ultrasonic extracts of E. coli 121/176 (an auxotroph requiring cobalamin or methionine for growth) cobalamin is essential even when H4PtG3 (or extract of heated E. coli) is present.…”

Interrelations Between Two Pathways of Methionine Biosynthesis in Aerobacter aerogenes

“…1). As observed with Escherichia coli PA 15 (Kisliuk & Woods, 1960) tetrahydropteroylglutamate did not promote methionine synthesis but tetrahydropteroyltriglutamate did reactivate the system (Jones, Guest & Woods, 1961). The additional requirements for the A. aerogenes system are shown in Table 3.…”

Mechanism of Methionine Biosynthesis in Rat Liver

“…Pteroyl-y-diglutamyl-y-glutamate was synthesized by the method of Boothe et al [S] and reduced as described by Jones and coworkers [9]. The Nj-[14C]methyl-derivative was prepared by a procedure identical with that for N5-methyl-H,PteGlu3 [ Other Analytical Procedures L-Phenylalanine was determined microbiologically with L. mesenteroides P 60 by the method of Steel et al [13].…”