Akemi Doi

ADP-D-glucose—α-1,4-glucan α-4-glucosyltransferase in spinach chloroplasts Partial purification and some properties of the enzyme

Summary 1. A soluble enzyme which transfers glucosyl residues from ADPglucose to α -1,4-glucan has been obtained from spinach chloroplasts and partially purified 2. Some properties of the enzyme such as pH optimum, temperature optimum, nucleotide specificity, effectiveness of primers, etc ., have been investigated. Sulfhydryl groups may be important in the action of the enzyme 3. The present status of the enzyme in the research of starch biosynthesis is discussed.

ADP-D-glucose: α-1,4-glucan α-4-glucosyltransferase of spinach leaves Enzymatic synthesis of amylopectin-type polysaccharide in a two-enzyme system

Abstract Combined action of highly purified spinach α-glucan-ADP glucosyltransferase ADP- D -glucose: α-1,4-glucan α-4-glucosyltransferase and potato α-glucan-branching glycosyltransferase (EC 2.2.1.18) led to the formation of branched polysaccharide of a large molecular size. The synthetic polysaccharide was similar to natural amylopectin in the spectral characteristics of the iodine complex, in β-amylolysis limit and in the basal chain.

Cloning and nucleotide sequence of the CDC23 gene of Saccharomyces cerevisiae

As a preliminary step for studying the function and intracellular behavior of the product of the CDC23 gene, a cell cycle gene of Saccharomyces cerevisiae, we cloned the CDC23 gene and determined its nucleotide (nt) sequence. The nt sequence contains an open reading frame (ORF) of 1878 nt coding for a protein of 626 amino acids (aa). The CDC23 gene is expressed as a 2.4- to 2.5-kb major transcript. The putative protein product of the CDC23 gene has a potential Ca2(+)-binding site near its N terminus, and has four contiguous repeats of a consensus sequence consisting of 34 aa near its C terminus. Regions that can be regarded as consisting of repeats of the same consensus sequence were found in the published aa sequences of the products of three other yeast genes.

Progress in the mitotic cycle of yeast spheroplasts in liquid culture

Abstract When inoculated into a rich medium with standard concentrations of nutrients at a sufficiently low cell density, spheroplast cells prepared from synchronized cells of Saccharomyces cerevisiae IFO 0971 carried synchronously out at least two successive rounds of DNA synthesis and nuclear division. Spheroplast cells performed their first round of DNA synthesis during roughly the same time as did normal cells, but entered the first round of nuclear division significantly later than normal cells. Following this first round, spheroplast cells initiated the second round of DNA synthesis without significant delay, but entered the second round of nuclear division again with significant delay compared with normal cells. The seemingly specific delay in initiating nuclear division in the mitotic cycle of spheroplast cells cultivated in this medium increased linearly as the medium was diluted with respect to nutrient concentration. Addition of d -glucose (but not of l -glucose) to a diluted medium partially suppressed the increasing delay in initiating nuclear division in spheroplast cells cultivated in such a medium. In contrast to spheroplast cells, the timing of nuclear division initiation in the mitotic cycle of normal cells did not vary with the degree of dilution of the medium. Addition of hydroxyurea to a spheroplast culture which had completed the first round of DNA synthesis did not prevent (most) cells from commencing nuclear division, and spheroplast cells of such a culture displayed sedimentation patterns of newly synthesized DNA strands characteristic of a full-sized material, indicating that spheroplast cells in liquid culture complete DNA replication early in the mitotic cycle. On the basis of these results we propose that in spheroplast cells the potential to carry out a reaction(s) specifically involved in the initiation of nuclear division is at a lower level than that of normal cells. The expression of this potential is believed to be governed by the concentration of nutrients in the surrounding medium due to the reduced capacity of the cells to take up nutrients, when compared with the capacity of normal cells.