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Simple and reliable protocols are described for an extensive analysis of metabolites in extracts from different biological sources. The separation was performed by high performance ionic-exchange chromatography (HPIC) at alkaline pH using two types of chromatography columns and two detection methods. Organic acids and inorganic anions were separated on an ionPac AS11 column using a 0.5 to 35 mM Na0H gradient. Detection limits in the range of milligrams per liter were achieved by use of a conductivity detector equipped with an anion self-regenerating suppressor. Twelve phosphorylated compounds belonging to the glycolytic and the pentose phosphate pathways could be resolved on a CarboPac PA1 column using a Na0H/Na-acetate gradient. Quantification was achieved by pulsed amperometry with detection limits in the micromolar range. Cell extracts obtained by extraction in boiling buffered ethanol described previously could be directly injected onto HPIC columns for the separation of metabolites because the extraction procedure affected neither the retention time nor the stability of most of the metabolites, and yielded very clean chromatograms. These improved protocols were applied for a dynamic analysis of intracellular metabolites in Saccharomyces cerevisiae in response to a glucose pulse. 相似文献
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A novel intracellular cycloalternan-degrading enzyme (CADE) was purified to homogeneity from the cell pellet of Bacillus sp. NRRL B-21195. The enzyme has a molecular mass of 125 kDa on SDS-PAGE. The pH optimum was 7.0, and the enzyme was stable from pH 6.0 to 9.2. The temperature optimum was 35 degrees C and the enzyme exhibited stability up to 50 degrees C. The enzyme hydrolyzed cycloalternan [CA; cyclo(-->6)-alpha-d-Glcp-(1-->3)-alpha-d-Glcp-(1-->6)-alpha-d-Glcp-(-->3)-alpha-d-Glcp-(1-->)] as the best substrate, to produce only isomaltose via an intermediate, alpha-isomaltosyl-(1-->3)-isomaltose. This enzyme also hydrolyzed isomaltosyl substrates, such as panose, alpha-isomaltosyl-(1-->4)-maltooligosaccharides, alpha-isomaltosyl-(1-->3)-glucose, and alpha-isomaltosyl-(1-->3)-isomaltose to liberate isomaltose. Neither maltooligosaccharides nor isomaltooligosaccharides were hydrolyzed by the enzyme, indicating that CADE requires alpha-isomaltosyl residues connected with (1-->4)- or (1-->3)-linkages. The K(m) value of cycloalternan (1.68 mM) was 20% of that of panose (8.23 mM). The k(cat) value on panose (14.4s(-1)) was not significantly different from that of cycloalternan (10.8 s(-1)). Judging from its specificity, the systematic name of the enzyme should be cycloalternan isomaltosylhydrolase. This intracellular enzyme is apparently involved in the metabolism of starch via cycloalternan in Bacillus sp. NRRL B-21195, its role being to hydrolyze cycloalternan inside the cells. 相似文献
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Ragon M Aumelas A Chemardin P Galvez S Moulin G Boze H 《Applied microbiology and biotechnology》2008,78(1):47-53
Debaryomyces castellii phytase was purified to homogeneity in a single step by hydrophobic interaction chromatography. Its molecular mass is 74 kDa
with 28.8% glycosylation. Its activity was optimal at 60°C and pH 4.0. The K
m value for sodium phytate was 0.532 mM. The enzyme exhibited a low specificity and hydrolyzed many phosphate esters. The phytase
fully hydrolyzed myo-inositol hexakisphosphate (or phytic acid, Ins P6) to inositol and inorganic phosphate. The sequence of Ins P6 hydrolysis was determined by combining results from high-performance ionic chromatography and nuclear magnetic resonance.
D. castellii phytase is a 3-phytase that sequentially releases phosphate groups through Ins (1,2,4,5,6) P5, Ins (1,2,5,6) P4, Ins (1,2,6) P3, Ins (1,2) P2, Ins (1 or 2) P1, and inositol (notation 3/4/5/6/1 or 2). 相似文献
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