Iterative highly reducing polyketide synthases from filamentous fungi are the most complex and enigmatic type of polyketide synthase discovered to date. Here we uncover an unusual degree of programming by the hypothemycin highly reducing polyketide synthase, in which a single ketoreductase domain shows stereospecificity that is controlled by substrate length. Mapping of the structural domains r...

In a study of minimal requirements for certain lactobacilli, Leuconostoc dextranicum 8086 was observed to require either aspartic acid or threonine for growth in a particular medium. Since such an observation does not allow specific conclusions regarding the relationship of these two amino acids, a study of this interrelationship in lactobacilli in which aspartic acid biosynthesis can be contro...

The biosynthesis and macromolecular organization of proteoglycans was studied in explants of adult human articular cartilage. In a series of pulse-chase experiments, labelling with (35S)sulphate, it was shown that the proteoglycan monomer is synthesized as a precursor that has a low affinity for hyaluronic acid. These findings suggest a possible mechanism by which the rate of incorporation of p...

In a study of minimal requirements for certain lactobacilli, Leuconostoc dextranicum 8086 was observed to require either aspartic acid or threonine for growth in a particular medium. Since such an observation does not allow specific conclusions regarding the relationship of these two amino acids, a study of this interrelationship in lactobacilli in which aspartic acid biosynthesis can be contro...

Tissue cultures o f Pimpinella anisum and P. major were used to study the biosynthesis o f pseudoisoeugenols. The putative precursors were labelled with 13C with one exception that was labelled with i4C. The incorporation o f the label was controlled by 13C N M R and liquid scintil­ lation, respectively. The biosynthetic sequence found was L-phenylalanine, /-cinnamic acid, /?-coumaric acid, / 7...

mutations in separate loci. A comparison of the present findings with those of Demerec has shown that the four phenotypic groups are identical with the four transduction classes, which suggests that each group is characterized by a block in one of the steps of tryptophan biosynthesis and that each block is produced by mutation in one gene locus. The data are therefore consistent with the follow...

Leaf-color mutants in rice (Oryza sativa L.) are excellent models for studying chlorophyll biosynthesis and chloroplast development. In this study, a yellow-green-leaf mutant generated by 60Co irradiation, ygl9311, was isolated: it displayed yellow-green leaf phenotype during the complete growth cycle. Compared with wild type, photosynthetic pigment contents of leaves ygl9311 were significantly...

During its reduction to water, O2 readily gives rise to dangerously reactive intermediates. This threat is diminished by families of defensive enzymes which include the superoxide dismutases, catalases and peroxidases. Free radical chain reactions are controlled by antioxidants, such as ascorbate and the tocopherols, and oxidative damage, which occurs in spite of these defenses, is largely repa...

A B S T R A C T By using a methylcellulose clonal assay, we cultured peripheral blood erythropoietic precursors from a patient with sickle cell anemia, a patient with sickle cell hemoglobin C disease, and a normal volunteer. We then analyzed the synthetic rates ofadult and fetal hemoglobins (Hb) in individual erythropoietic bursts. Hb were labeled with '4C-amino acids in culture, separated by s...

Auxin acts synergistically with cytokinin to control the shoot stem-cell niche, while both hormones act antagonistically to maintain the root meristem. In aluminum (Al) stress-induced root growth inhibition, auxin plays an important role. However, the role of cytokinin in this process is not well understood. In this study, we show that cytokinin enhances root growth inhibition under stress by m...