Inhibition of Recombinant Aldose-6-Phosphate Reductase from Peach Leaves by Hexose-Phosphates, Inorganic Phosphate and Oxidants.

Glucitol, also known as sorbitol, is a major photosynthetic product in plants from the Rosaceae family. This sugar alcohol is synthesized from glucose-6-phosphate by the combined activities of aldose-6-phosphate reductase (Ald6PRase) and glucitol-6-phosphatase. In this work we show the purification and characterization of recombinant Ald6PRase from peach leaves. The recombinant enzyme was inhibited by glucose-1-phosphate, fructose-6-phosphate, fructose-1,6-bisphosphate and orthophosphate. Oxidizing agents irreversibly inhibited the enzyme and produced protein precipitation. Enzyme thiolation with oxidized glutathione protected the enzyme from insolubilization caused by diamide, while incubation with NADP+ (one of the substrates) completely prevented enzyme precipitation. Our results suggest that Ald6PRase is finely regulated to control carbon partitioning in peach leaves.

Involvement of the macrophage mannose-6-phosphate receptor in the recognition of Leishmania mexicana amazonensis.

Significant differences were found in the ability of resident mouse peritoneal macrophages to ingest amastigote and promastigote forms of Leishmania mexicana amazonensis. Differences in the association index of the parasites to the macrophages were also found between infective and non-infective promastigotes. Evidence was obtained suggesting that the macrophage receptor, which recognizes mannose-6-phosphate-containing units found in lysosomal enzymes, is involved in the association with the macrophage of promastigotes, but not of amastigotes. Addition of mannose-6-phosphate, its structural analogue fructose-1-phosphate, Hansenula holstii phosphomannan or the mannose-6-phosphate-containing lysosomal enzyme alpha-D-mannosidase to the interaction medium, markedly inhibits the association of the parasites with macrophages.

Fructose catabolism in Azospirillum brasilense and Azospirillum lipoferum.

The pathways for catabolism of fructose were investigated in the type strains of Azospirillum lipoferum and Azospirillum brasilense grown aerobically with (NH4)2SO4 as the nitrogen source. When grown on fructose, the former species possessed a complete Entner-Doudoroff pathway, whereas the latter species lacked activity for glucose-6-phosphate dehydrogenase. Both species possessed a complete catabolic Embden-Meyerhof-Parnas pathway. Neither species possessed the key enzyme of the hexose monophosphate pathway, 6-phosphogluconate dehydrogenase. Both species could phosphorylate fructose to fructose-1-phosphate by means of a phosphoenolpyruvate-phosphotransferase system, and high activities of 1-phosphofructokinase occurred. Both species possessed glucokinase activity, but only A. lipoferum had hexokinase activity; moreover, the cells of A. brasilense were nearly impermeable to glucose, accounting for the inability of this species to grow on glucose. Both species possessed pyruvate dehydrogenase, a complete tricarboxylic acid cycle, a glyoxylate shunt, and malic enzyme. Analysis of the acidic end products for both species indicated the formation of only small amounts of various organic acids, and most of the titratable acidity was due to utilization of the ammonium ions of the medium. Gluconic acid was not formed during growth of either species on fructose but was detected during growth of A. lipoferum on glucose; this species also possessed an NADP-linked glucose dehydrogenase and gluconokinase.

Metabolism of various carbon sources by Azospirillum brasilense.

Azospirillum brasilense Sp7 and two mutants were examined for 19 carbon metabolism enzymes. The results indicate that this nitrogen fixer uses the Entner-Doudoroff pathway for gluconate dissimilation, lacks a catabolic but has an anabolic Embden-Meyerhof-Parnas hexosephosphate pathway, has amphibolic triosephosphate enzymes, lacks a hexose monophosphate shunt, and has lactate dehydrogenase, malate dehydrogenase, and glycerokinase. The mutants are severely deficient in phosphoglycerate and pyruvate kinase and also have somewhat reduced levels of other carbon enzymes.

Leukocyte glutathione peroxidase deficiency in a male patient with chronic granulomatous disease.

A male child with chronic granulomatous disease is described in whom glutathione peroxidase deficiency of leukocytes was identified. Stability and activity of G-6-PD and activity of NADPH oxidase were normal. The leukocytes of the parents showed intermediate activities of glutathione peroxidase, suggesting the possibility of autosomal recessive inheritance.

Chronic granulomatous disease in an adult male: A proposed X-linked defect.

A 25-year old patient with chronic granulomatous disease of somewhat unusual history is described. The diagnosis of CGD was based on increased susceptibility to infection, granulomatous appearance of tissues, and diminished bactericidal and metabolic response of leukocytes during phagocytosis: the clinical and cellular features considered phenotypic of CGD. A 16-year-old female sibling had bactericidal and metabolic abnormalities of leukocyte function similar to those of the patient's leukocytes. Leukocytes from another sister, 26 years of age, were intermediate in bactericidal capacity. Two populations of leukocytes were identified by a histochemical test of NBT reduction. Both normal and abnormal polymorphonuclear leukocytes were present in the leukocyte population of the two sisters. Leukocytes from the patient's mother and maternal grandmother were normal by all methods tested. These findings are taken as evidence of a germ-line mutation in the chromosomal gene causing CGD, with transmission of the genetic defect from the mother to the son.