The biosynthesis of chromomycin A3 was investigated using 13C-labeled acetates, methionine and glucose, and 13C,18O-labeled acetate. 13C NMR spectral analysis demonstrated that: Aglycone assembly occurs by combining at least two polyketide chains; three of nine oxygen atoms of the aglycone originate from acetate precursor oxygen atoms; carbon methylations on the aromatic ring at C-7, on the chr...

When isolated nuclei from 12-day-old rat brains were incubated with S-adenosyl-L-[methyl-3H]methionine, significant amounts of 3H-methyl were incorporated into lysyl residues in histones H3 and H4. About 0.024% of the total methylation sites on histone H3 and 0.013% of the sites on histone H4 were unmethylated at the time the nuclei were isolated. Methylation of these sites proceeded stepwise, ...

inhibited by S-adenosyl-L-ethionine. The endogenous methyltransferase was able to transfer ethyl groups from the latter compound to histone but with very low efficiencycompared to the arginine methyltransferase reported previ ously. The histone lysine methyltransferase has a Km value of 3.0 /IM, and the K, value for S-adenosylethionine inhibition is 0.17 mM. Product inhibition by S-adenosylhomo...

The effects of varying concentrations of L-methionine, L-homocysteine, and adenosine on the tissue levels of S-adenosylmethionine (AdoMet) and S-adenosyl-homocystein (AdoHcy) were investigated in perfused liver. In the normal liver, the intracellular concentration of AdoMet was dependent upon the availability of methionine. In the presence of high concentrations of methionine the maximum level ...

Cytokinins (CKs), a class of phytohormones that regulate plant growth and development, are also synthesized by some phytopathogens to disrupt the hormonal balance and to facilitate niche establishment in their hosts. Rhodococcus fascians harbors the fasciation (fas) locus, an operon encoding several genes homologous to CK biosynthesis and metabolism. This pathogen causes unique leafy gall sympt...

The enzymatic activities for the synthesis of phosphatidylcholine from phosphatidylethanolamine and Sadenosyl-L-methionine have been solubilized from rat liver microsomes by ultrasonic disruption in the presence of 0.2% Triton X-100. Significant co-purification of the activities was achieved by chromatography of the Triton extract on octyl-Sepharose CL-4B and, subsequently, on Sepharose 6B. Thr...

An in vitro system was used to study DNA synthesis in lysates of Escherichia coli cells which had been grown in the presence of ethionine. Such lysates showed a reduced capacity to incorporate [3H]TTP into high-molecular-weight material. Activity could be restored by incubation with S-adenosyl methionine and ATP. S-adenosyl methionine-reactivated TTP incorporation required the presence of DNA p...

An enzymatic reaction has been identified in the isthmus of hen oviduct in which sulfate is transferred from 3’-phosphoadenosine 5’-phosphosulfate to mucopolysaccharide acceptors (1). From studies of the reaction with monosaccharides and oligosaccharides as model acceptors (‘2) it was concluded that one or more enzymes in the preparations employed catalyze a direct transfer of sulfate from PAPS...

Human red blood cells reach an equilibrium of phosphate distribution at 37 ° much faster with o . I I M or intermediate levels than with o.o2 M and lower phosphate levels. Other divalent anions added to 0.o2 M phosphate solutions have an action similar to that of the extra phosphate. A past observation that phosphate escapes from red cells more slowly than it enters them appears to have arisen ...

During the past few years, the IRBIT domain has emerged as an important add-on of S-adenosyl-L-homocystein hydrolase (AHCY), thereby creating the new family of AHCY-like proteins. In this review, we discuss the currently available data on this new family of proteins. We describe the IRBIT domain as a unique part of these proteins and give an overview of its regulation via (de)phosphorylation an...