The effects of calystegines isolated from edible fruits and vegetables on mammalian liver glycosidases

The polyhydroxylated nortropane alkaloids called calyste-ginesoccur in many plants of the Convolvulaceae, Solanaceae, andMoraceae families. Certain of these alkaloids exhibit potentinhibitory activities against glycosidases and the recentlydemonstrated occurrence of calystegines in the leaves, skins,and sprouts of potatoes (Solatium tuberosum), and in the leavesof the eggplant (S.melongena), has raised concerns regardingthe safety of these vegetables in the human diet. We have surveyedthe occurrence of calystegines in edible fruits and vegetablesof the families Convolvulaceae, Solanaceae, and Moraceae byGC-MS. Calystegines A3, B1, B2, and C1 were detected in allthe edible fruits and vegetables tested; sweet and chili peppers,potatoes, eggplants, tomatoes, Physalis fruits, sweet potatoes,and mulberries. Calystegines B1 and C1 were potent competitiveinhibitors of the bovine, human, and rat β-glucosidaseactivities, with K₁ values of 150, 10, and 1.9 µM, respectivelyfor B1 and 15,1.5, and 1 µM, respectively, for C1. CalystegineB2 was a strong competitive inhibitor of the -galactosidaseactivity in all the livers. Human β-xylosidase was inhibitedby all four nortropanes, with calystegine C1 having a K₁ of0.13 µM. Calystegines A3 and B2 selectively inhibitedthe rat liver β-glucosidase activity. The potent inhibitionof mammalian β-glucosidase and -galactosidase activitiesin vitro raises the possibility of toxicity in humans consuminglarge amounts of plants that contain these compounds. edible plants calystegines glycosidase inhibitors bovine, human, and rat liver     

Isolation and characterization of a molecular chaperone, gp57A, of bacteriophage T4.

A molecular chaperone of bacteriophage T4, gp57A, which facilitates the formation of the long and short tail fibers, was isolated and characterized by peptide analysis, sedimentation equilibrium, and circular dichroism (CD). Sequence analysis confirmed the predicted sequence of 79 amino acids from the nucleotide sequence of the gene with the N-terminal methionine removed. The result led to the conclusion that the apparent smaller molecular weight of 6,000 from Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis than the expected molecular weight of 8,710 was due to its abnormal electrophoretic behavior instead of cleavage or processing of the gene product. Estimation of the secondary structure from far-UV CD indicated a 94% alpha-helix content, which was in accord with the prediction from the primary structure. A sedimentation equilibrium study, on the other hand, revealed that gp57A assumes a tetrameric subunit structure.     

Changes of an androgen-dependent nuclear protein during functional differentiation and by dedifferentiation of the dorsolateral prostate of rats

In contrast with previous results that indicate that Saccharomyces cerevisiae fructose-1,6-bisphosphatase is a dimer of 56,000 molecular weight subunits, we find that the subunit Mr of the enzyme purified from baker's yeast is 40,000. The same subunit Mr was observed in immunoprecipitates of crude supernatants of baker's yeast and S. cerevisiae cultures, as well as in acid-extracts of cells detected by immunoblotting, suggesting that the native subunit indeed has a Mr of 40,000 and it has not been produced from a larger polypeptide. Complete immunoprecipitation of fructose-1,6-bisphosphatase activity with saturating concentrations of specific antibody suggests that there is only one fructose-1,6-bisphosphatase isozyme in S. cerevisiae. The Mr of the purified enzyme determined by size exclusion HPLC suggests that it has a tetrameric structure characteristic of fructose-1,6-bisphosphatases from a broad phylogenetic spectrum.     

High-performance liquid chromatographic determination of hippuric acid in human urine

A method is described for the determination of urinary hippuric acid by high-performance liquid chromatography. The method used ethyl acetate extraction for partial clean-up of the urine. The separation was carried out on a reversed-phase column using 20% methanol in 0.01 M aqueous potassium phosphate containing 0.5% acetic acid as a mobile phase. The column effluent was monitored with a UV detector at 254 nm. Hippuric acid was separated from other normal urine constituents in less than 10 min. Metabolites of xylene and styrene did not interfere with the assay. Analytical recoveries from urine were excellent and peak height and concentration were linearly related.     

Increase in acetylation of spermidine in rat liver extracts brought about by treatment with carbon tetrachloride

Within three hours of the administration of hepatotoxic doses of carbon tetrachloride to rats there was a substantial increase in the ability of liver extracts to catalyze the accumulation of monoacetylspermidine when incubated with spermidine and acetyl-CoA. This increase was maximal by six hours and correlated with the period in which there was a pronounced fall in hepatic spermidine and concomitant increase in putrescine. During this time there is a large increase of the conversion of labeled spermidine into putrescine in the liver. These results therefore suggest that this conversion requires the prior acetylation of spermidine.     

Quantitative conservation of chromatin-bound RNA polymerases I and II in mitosis. Implications for chromosome structure

RNA synthesis almost ceases in mitosis. It is ambiguous whether this temporal, negative control of RNA synthesis is solely because of the nature of chromosomes per se, (i.e., their condensed state), or to a physical loss of RNA polymerases along with other nuclear proteins which have been shown to pass into the cytoplasm in mitosis, or to their combined feature. Aside from such regulatory considerations, a question has also been raised as to whether RNA polymerases are constituents of metaphase chromosomes. To clarify these aspects of RNA polymerase-chromatin interaction in mitosis, the enzymes in chromosomes were quantitated and their levels compared to those in interphase nuclei and cells at various phases of the cell cycle. The results show that the amounts of form I, form II, and probably form III enzymes bound to a genome-equivalent of chromatin stay constant during the cell cycle. Thus, the mechanism for the negative control of RNA synthesis in mitosis appears to exist in the chromosomes per se, but not to be directly related to the RNA polymerase levels. This quantitative conservation of chromatin-bound RNA polymerases implies that they may persist as structural components of the chromosomes in mitosis.     

Synthetic gibberellin synergists in elongation of shoot growth ofOryza sativa L.

Previous studies showed that 2-ethyl-3-methoxycarbonyl-1-(p-tolylcarbamoyl) isourea acts as a potent GA₃-synergist in stimulating shoot growth of rice seedlings. Studies with several structurally related compounds show that the alkoxycarbonylcarbamoyl-isourea or -isothiourea skeleton is required for biological activity. Any chemical deletion from this skeleton causes complete loss of activity. From present and previous data it seems that alkoxycarbonylcarbamoyl-isourea or -isothiourea is converted by intramolecular cyclization in the rice seedlings into the corresponding triazinone that serves as the active form.Part 9 in the series Plant Growth-regulating Activities of Isourea Derivatives and Related Compounds; for Part 8 seeReferences, Ogawa et al. (1980b)     

Synthetic gibberellin synergists in elongation of shoot growth ofOryza sativa L.

Previous studies showed that 2-ethyl-3-methoxycarbonyl-1-(p-tolylcarbamoyl) isourea acts as a potent GA₃-synergist in stimulating shoot growth of rice seedlings. Studies with several structurally related compounds show that the alkoxycarbonylcarbamoyl-isourea or -isothiourea skeleton is required for biological activity. Any chemical deletion from this skeleton causes complete loss of activity. From present and previous data it seems that alkoxycarbonylcarbamoyl-isourea or -isothiourea is converted by intramolecular cyclization in the rice seedlings into the corresponding triazinone that serves as the active form.