Auricularia cornea (E.) polysaccharide is an important component of A. cornea Ehrenb, a white mutant strain of Auricularia with biological activities, such as enhancement of human immune function and cancer prevention. The hyaluronic acids (HAs) are important components of the A. cornea polysaccharide and have extremely high medicinal value. In this study, we used HA to search the target protein sucrase-isomaltase (SI). In addition, we also performed molecular dynamics (MD) simulations to explore the binding of three inhibitors (HA, acarbose and kotalanol) to SI. The MD simulations indicated that the binding of the three inhibitors may induce the partial disappearance of α helix in residues 530-580. Hence, the hydrogen bond for Gly570-Asn572, which was near the catalytic base Asp471 in SI, was broken during the binding of the three inhibitors. We reveal a new inhibitor for SI and provide reasonable theoretical clues for inhibitor binding to SI.

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OBJECTIVE: To improve heterologous proteins production, we constructed a maltose-inducible expression system in Bacillus subtilis.
RESULTS: An expression system based on the promoter for maltose utilization constructed in B. subtilis. Successively, to improve the performance of the P malA -derived system, mutagenesis was employed by gradually shortening the length of P malA promoter and altering the spacing between the predicted MalR binding site and the -35 region. Furthermore, deletion of the maltose utilization genes (malL and yvdK) improved the P malA promoter activity. Finally, using this efficient maltose-inducible expression system, we enhanced the production of luciferase and D-aminoacylase, compared with the P hpaII system.
CONCLUSIONS: A maltose-inducible expression system was constructed and evaluated. It could be used for high level expression of heterologous proteins production.

BACKGROUND: Congenital sucrase-isomaltase deficiency (CSID) is a rare genetic disorder. The prevalence of CSID in Chinese population is unknown and no single case has been reported.
METHODS: Sucrose tolerance tests were performed in three children suspected of CSID. Glucose tolerance tests were performed to exclude glucose malabsorption. Blood glucose was measured at fasting and at 30 min, 60 min, 120 min, and 180 min of the study. Gastrointestinal symptoms were recorded up to 4 hours after the study.
RESULTS: From December 2008 to June 2011, three children, ranging from 16 to 19 months old, were referred to our tertiary children\'s hospital due to chronic watery diarrhea and failure to thrive. Laboratory investigations including complete blood counts, ESR, CRP, and serum immunoglobulins were normal. Routine stool culture for bacteria and exam for parasites were negative. Upper endoscopy, colonoscopy and histology were unremarkable. All children failed lactose-free and amino acid-based formulas. All three children had flat sucrose tolerance tests and began to have watery stool 2-4 hours after feeding sucrose test solution. The glucose tolerance tests were normal and no children developed watery stools up to 4 hours after feeding glucose test solution.
CONCLUSIONS: This is the first case series of CSID in Chinese children. The diagnosis of CSID can be made based on clinical suspicion and sucrose tolerance test. CSID is probably an under-diagnosed or misdiagnosed disease in Chinese children and should be considered in children with chronic watery diarrhea.

Breaking the balance between proliferation and differentiation in animal cells can lead to cancer, but the mechanisms maintaining this balance remain largely undefined. The calcium activated chloride channel A1 (CLCA1) is a member of the calcium sensitive chloride conductance family of proteins and is expressed mainly in the colon, small intestine and appendix. We show that CLCA1 plays a functional role in differentiation and proliferation of Caco-2 cells and of intestinal tissue. Caco-2 cells spontaneously differentiate either in confluent culture or when treated with butyrate, a molecule present naturally in the diet. Here, we compared CLCA1 expressional levels between patients with and without colorectal cancer (CRC) and determined the functional role of CLCA1 in differentiation and proliferation of Caco-2 cells. We showed that: 1) CLCA1 and CLCA4 expression were down-regulated significantly in CRC patients; 2) CLCA1 expression was up-regulated in Caco-2 cells induced to differentiate by confluent culture or by treatment with sodium butyrate (NaBT); 3) Knockdown of CLCA1 with siRNA significantly inhibited cell differentiation and promoted cell proliferation in Caco-2 confluent cultures, and 4) In Caco-2 3D culture, suppression of CLCA1 significantly increased cell proliferation and compromised NaBT-induced inhibition of proliferation. In conclusion, CLCA1 may contribute to promoting spontaneous differentiation and reducing proliferation of Caco-2 cells and may be a target of NaBT-induced inhibition of proliferation and therefore a potential diagnostic marker for CRC prognosis.

Clinical reports have demonstrated that berberine is a potential antidiabetic agent, but the underlying mechanism is unclear. The purpose of this study was to investigate if berberine exerts its hypoglycemic action via inhibiting intestinal disaccharidases using in vivo and in vitro experiments. Streptozotocin-induced diabetic rats received berberine (100 or 200 mg/kg) orally once daily or acarbose (40 mg/kg) orally twice daily for 5 weeks. Disaccharidase activities and sucrase-isomaltase (SI) complex messenger RNA (mRNA) expression in intestinal regions were assessed. The same treatment was operated in normal rats. Sucrose and maltose loading tests were also documented. In addition, Caco-2 cells were cultured in medium containing berberine or berberine plus chelerythrine. Compound C or H-89 for 5 days, disaccharidase activities, and SI complex mRNA levels were measured. The animal experiments showed that berberine significantly decreased the disaccharidase activities and SI complex mRNA expression both in diabetic rats and normal rats. Berberine can also significantly lower postprandial blood glucose levels induced by sucrose or maltose loading in normal rats. The cellular results showed that berberine may suppress disaccharidase activities and downregulate SI complex mRNA expression in a concentration-dependent manner. Only H-89, an inhibitor of protein kinase A (PKA), may reverse the decrease in disaccharidase activities and SI complex mRNA expression induced by berberine. In conclusion, berberine suppresses disaccharidase activities and SI complex mRNA expression with beneficial metabolic effects in diabetic states. The inhibitory effect, at least partly, involves the PKA-dependent pathway.