Properties of an inhibitor of trehalase in trehalaseless mutants of Neurospora

Synthesis and Antifungal Activities of Glucosamine Aromatic Derivatives Against Four Phytopathogenic Fungi of Crops

A series of diversified glucosamine derivatives (3a-3y) was synthesized and their antifungal activity was examined against four kinds of phytopathogens, Fusarium graminearum (F. graminearum), Fusarium moniliforme (F. moniliforme), Curvularia. lunata (C. lunata), and Rhizoctonia solani (R. solani) which cause seriously economic losses worldwide by affecting crops. The compound 3o showed remarkable antifungal activity against F. graminearum with EC50 value of 3.96 μg/mL, compared to the standard drug triadimefon (10.1 μg/mL). 3D-QSAR model with the statistically recommended values (r2=0.915, q2=0.872) showed that positive charge group or bulky group in the benzyl ring was favorable for the antifungal activity. Enzyme activity assays confirmed that 3o had a moderate inhibition of trehalase with inhibition rate of 51.4 % at 5 μg/mL, which is comparable to those of commercial inhibitor validamycin A with inhibition rate of 83.3 %. Molecular docking analysis revealed that 3o also had a hydrogen bond interaction with key amino acid residue compared to validoxylamine.

Comparative studies of suidatrestin, a specific inhibitor of trehalases

Suidatrestin, isolated from a Streptomyces strain, was characterized as a new trehalase inhibitor. Its inhibitory potential was 7 to 50-fold higher than that of validamycin when tested against insect, fungal and mammalian trehalases. The kinetic properties of suidatrestin were studied in vitro with trehalases from flight muscle mitochondria of the fly, Protophormia terraenovae, from larval midgut of the moth, Spodoptera littoralis, and from porcine kidney, as well as with maltase from yeast. Suidatrestin was inactive on maltase but inhibited all trehalases with IC50 values of 0.08-0.1 microM; Ki values ranged from 0.02 to 0.05 microM. The very low Ki/K(m) ratios (3.9 x 10(-6) -4.9 x 10(-6)) indicated excellent in vitro inhibitory action of suidatrestin. When injected into larvae of S. littoralis, suidatrestin required high and repetitive doses which lead to reversible inhibition of larval growth only. Consecutive omission of the inhibitor even stimulated weight increase above that of controls. Significant mortality was achieved at a rather high dose only. Injection of a growth-inhibiting dose of suidatrestin did not change hemolymph osmolality as a measure of sugar concentration. The discrepancy between in vitro and in vivo potency of suidatrestin may be understood once its chemical structure is fully known.

The control of saccharide synthesis during development of Myxamoebae of Dictyostelium discoideum containing differing amounts of glycogen

1. Myxamoebae initially containing 5.59mg of glycogen/10(8) cells accumulate approx. 25% more cell-wall polysaccharide, 100% more mucopolysaccharide, 200% more glucose and 300% more trehalose during their development than do myxamoebae initially containing less than 0.3mg of glycogen/10(8) cells. 2. These observations restrict the number of possible control mechanisms operating to regulate carbohydrate metabolism during development. 3. Cells accumulating a large amount of trehalose (approx. 400mug/10(8) cells) have the same amount and pattern of changes in specific activity of trehalase and trehalose 6-phosphate synthase as do cells accumulating a smaller amount of trehalose (approx. 100mug/10(8) cells). 4. These two populations of cells do, however, differ markedly in the amount of UDP-glucose and glucose 6-phosphate that they contain. 5. It is concluded that this change in the intracellular pools of the metabolic precursors of trehalose accounts for the increased amount of trehalose synthesized by cells derived from myxamoebae containing an increased glycogen content.