Yoshiko Yokote

Possible Link between Glycolysis and Apoptosis Induced by Sodium Fluoride

Fluoride has been used to prevent caries in the dentition, but the possible underlying mechanisms of cytotoxicity induction by this compound are still unclear. Since fluoride is known as an inhibitor of glycolytic enzymes, we investigated the possible connection between NaF-induced apoptosis and glycolysis in human promyelocytic leukemia HL-60 cells. NaF-induced apoptotic cell death is characterized by caspase activation, internucleosomal DNA fragmentation, loss of mitochondrial membrane potential, and production of apoptotic bodies. Higher activation of caspases-3 and -9, as compared with that of caspase-8, suggested the involvement of an extrinsic pathway. Utilization of glucose was nearly halted by NaF, whereas that of glutamine was rather enhanced. NaF enhanced the expression of Bad protein, but not that of Bcl-2 and Bax proteins, and reduced HIF-1α mRNA expression. Analysis of these data suggests a possible link between glycolysis and apoptosis.

Recovery of tryptophan from 25-minute acid hydrolysates of protein

It was found that thioglycolic acid prevents destruction of tryptophan during rapid hydrolysis of protein with a trifluoroacetic acid/HCl mixture (1:2, v/v) at 166 degrees C for 25 or 50 min. The addition of 5% (v/v) thioglycolic acid gave the maximum tryptophan recovery (88.3%) for a 25-min hydrolysate of lysozyme. Tryptophan recoveries varied slightly among three different proteins; 88% for lysozyme, 73% for alpha-chymotrypsinogen A, and 85% for apomyoglobin. However, when extrapolated to zero time, the values were close to one another: 94, 87, and 88%, respectively. The addition of thioglycolic acid was also advantageous for recovering amino acids other than tryptophan. Particularly, yields of carboxymethylcysteine and methionine were greatly improved. This modified rapid hydrolysis method gave satisfactory results without the need for separate analyses of tryptophan and cysteine, provided proteins were reduced and carboxymethylated prior to hydrolysis.

Interfacial behavior of fatty-acylated sericin prepared by lipase-catalyzed solid-phase synthesis

Fatty-acylated sericin {1:0.7 molar ratio of sericin (M r 18,700) to oleic acid} was prepared by lipase-catalyzed solid-phase synthesis in n-hexane containing oleic acid to endow sericin with interfacial properties. Acylation with oleic acid was confirmed by 1H-NMR. The fatty-acylated sericin exhibited superior emulsifying activity index and emulsion stability in the presence of 0–0.5 M NaCl, in a temperature range of 30–80 °C and pH range of 2–7, as compared with the control sericin. The fatty-acylated sericin (1:0.4 molar ratio) prepared by using low-molecular-weight sericin (M r 5,000) also exhibited superior emulsifying properties. The affinity of the fatty-acylated sericin to a hydrophobic surface as evaluated by a biomolecular interaction analyzer was about twice as much as that of the control sericin. The fatty-acylated sericin showed retarded water vaporization, similar to the control sericin, indicating good retention of moistness, and was adsorbed four times as much to defatted wool with little desorption as compared with the control sericin.

Thermal Behavior of Fowl Feather Keratin

Differential scanning calorimetry (DSC) was applied to elucidate the thermal behavior of fowl feather keratins (barbs, rachis, and calamus) with different morphological features. The DSC curves exhibited a clear and relatively large endothermic peak at about 110–160 °C in the wet condition. A considerable decrease in transition temperature with urea and its helical structure content estimated by Fourier transform infrared spectroscopy (FT-IR), and the disappearance of one of the diffraction peaks with heating at 160 °C for 30 min, indicated that DSC could be used to evaluate the thermal behavior of keratin. Barbs showed a lower denaturation temperature than rachis and calamus. The pulverized samples showed a slightly higher denaturation temperature than the native samples. In the dry condition, thermal transition occurred in a markedly higher temperature region close to 170–200 °C. It is hence concluded that fowl feather keratins have very high thermal stability, and that the elimination of water brings about even greater thermal stability.

The complete amino-acid sequence of cytoplasmic glycerol-3-phosphate dehydrogenase from Drosophila virilis

Abstract The amino-acid sequence of cytoplasmic glycerol-3-phosphate dehydrogenase ( sn -glycerol-3-phosphate: NAD + 2-oxidoreductase, EC 1.1.1.8) (αGPDH m form) from Drosophila virilis was determined by the sequencing of peptides produced by trypsin, chymotrypsin, and Staphylococcus aureus V8 proteinase digestion after cyanogen bromide cleavage. In addition, carboxyl terminal residues were determined by analysis of amino acids produced by carboxypeptidase treatment. The enzyme is composed of two identical subunits, each of which has 352 amino-acid residues and a molecular weight of 38925. The N-terminal residue of the enzyme is blocked. The comparison of Drosophila and rabbit muscle enzymes revealed that both enzymes share similar properties, such as dimeric structure, blocked N-terminal and molecular weight. Furthermore, the amino-acid sequencing showed that the rabbit muscle and Drosophila glycerol-3-phosphate dehydrogenases are homogeneous because they are 63% identical; this value is comparable to the similarity between cytochromes c from both animals, a protein known to be slow in evolutionary rate. There is, however, a marked difference in C-terminal sequence, the D. virilis enzyme having an extra tripeptide (-Gln-Thr-Leu) at the C-terminal end.

Reversible Thermal Transition of Soluble Branched Chains from Slightly Acid-treated Potato Starch

The reversible thermal transition of soluble branched starch chains prepared from slightly acid-treated potato starch granules (ATS) was investigated. Potato starch was immersed in 15% sulfuric acid to obtain ATS with a 1% hydrolysis rate. About half of the molecules of ATS, which spontaneously formed large aggregates with a mass of a few million daltons in aqueous solution, was fractionated and soluble branched starch chains with a relative molecular weight (M r) of 8.91×104 were obtained. Structural analysis indicated that the soluble branched starch chains consisted of three unit chains with M r 7,900 and 21 unit chains with M r 2,700. DSC and FT-IR measurements showed that the soluble branched starch chains underwent a reversible thermal transition, which is considered to be a helix-coil transition, during heating and cooling, but a debranched sample and β-limit dextrins showed substantially different thermal behavior, indicating the contribution of the ordered structure of the branched chains.