Xuefang Bai

Purification and identification of a ACE inhibitory peptide from oyster proteins hydrolysate and the antihypertensive effect of hydrolysate in spontaneously hypertensive rats

Oyster (Crassostrea talienwhanensis Crosse) proteins were produced from fresh oyster and subsequently digested with pepsin. The separations were performed with a Sephadex LH-20 gel filtration chromatography and a RP-HPLC. A purified peptide with sequence Val-Val-Tyr-Pro-Trp-Thr-Gln-Arg-Phe (VVYPWTQRF) was firstly isolated and characterized from oyster protein hydrolysate and its ACE inhibitory activity was determined with IC50 value of 66μmol/L in vitro. Stability study for ACE inhibitory activity showed that the isolated nonapeptide had the good heat and pH stability and strong enzyme-resistant properties against gastrointestinal proteases. Kinetic experiments demonstrated that inhibitory kinetic mechanism of this peptide was non-competitive and its Km and Ki values were calculated. The yield of this peptide from oyster proteins was 8.5%. Furthermore, the oyster protein hydrolysate (fraction II), prepared by pepsin treatment firstly exhibited antihypertensive activity when it was orally administered to spontaneously hypertensive rat (SHR) at a dose of 20mg/kg. These results demonstrated that the hydrolysate from oyster proteins prepared by pepsin treatment could serve as a source of peptides with antihypertensive activity.

Conversion of biomass into 5-hydroxymethylfurfural using solid acid catalyst

5-Hydroxymethylfurfural (HMF) was produced from monosaccharide (fructose and glucose), polysaccharide (inulin) and the Jerusalem artichoke juice by a simple one-pot reaction including hydrolysis and dehydration using solid acid under mild condition. Hydrated niobium pentoxide (Nb(2)O(5)·nH(2)O(2)) after pretreatment showed high catalytic activities for dehydration of mono- and polysaccharide to HMF at 433 K in water-2-butanol (2:3 v/v) biphasic system, giving high HMF yield of 89% and 54% from fructose and inulin, respectively. The HMF yield was up to 74% and 65% when inulin and Jerusalem artichoke juice were hydrolyzed by exoinulinase. The solid acid made the process environment-friendly and energy-efficient to convert carbohydrates into bio-fuels and platform chemicals.

Chitosan oligosaccharides protect mice from LPS challenge by attenuation of inflammation and oxidative stress

Sepsis and its derivative syndromes are major causes of morbidity and mortality in the intensive care unit. Recently, lots of studies have shown that the progression of sepsis is attributed to redox imbalance and overproduction of proinflammatory cytokines. In previous studies, we have reported the anti-oxidative and anti-inflammatory effects of chitosan oligosaccharides in vitro. In the light of these findings, we applied the model of sepsis to mice by LPS injection to investigate whether chitosan oligosaccharides have a protective effect on LPS-induced sepsis. We found that treatment by chitosan oligosaccharides not only attenuated organ dysfunction but also improved survival rate after LPS injection. To further understand how it works, we examined several proinflammatory markers including neutrophil infiltration in organs and TNF-α and IL-1β in serum, and found that these cytokines were significantly reduced by chitosan oligosaccharide treatment. In addition to this, anti-oxidants including glutathione (GSH) and catalase (CAT) levels were depleted and malondialdehyde (MDA) levels were increased in LPS-induced sepsis, while chitosan oligosaccharides smoothed out the redox imbalance. Furthermore, we also assessed c-Jun NH(2)-terminal kinase and p38 mitogen-activated protein kinase signal activation by LPS-stimulation, and found both of them were attenuated by chitosan oligosaccharide treatment. Collectively, our data demonstrated that chitosan oligosaccharides can protect mice from the LPS challenge by virtue of anti-inflammatory effects as well as anti-oxidation properties, which might offer beneficial effects for patients with sepsis.

Molecular Cloning and Characterization of a Brassica napus L. MAP Kinase Involved in Oligochitosan-Induced Defense Signaling

Oligochitosan is a potent plant defense elicitor. In this paper, a novel Brassica napus mitogen-activated protein kinase (MAPK) gene induced by oligochitosan was isolated by rapid amplification of cDNA ends technique and designated as BnOIPK (oligochitosan-induced protein kinase (OIPK)). BnOIPK, with high sequence similarity to previously reported plant MAPK genes, encodes a 373-amino acid protein and belongs to the B subgroup of plant MAPK. Bioinformatics analysis showed BnOIPK contains one phosphorylation motif (TEY) and a conserved common docking domain in its C-terminal extension. With a constitutive expression in seedling leaves, BnOIPK is further upregulated upon treatment with plant hormone jasmonic acid (JA), but did not markedly respond to salicylic acid and abscisic acid. Activation of BnOIPK transcripts induced by oligochitosan depending on nitric oxide (NO) and hydrogen peroxide (H2O2) was identified by using NO, H2O2, and their scavenger, respectively. Polyclonal antibody BOK was prepared by using a 69-kD GST-BnOIPK fusion protein which was produced from pGEX-4T-1 vector. Western-blot assays showed BnOIPK could be induced by oligochitosan and JA at a short time. All these results suggest that BnOIPK might be a key node of JA-mediated defense signaling and act on the downstream of NO and H2O2.

Chitosan Oligosaccharides Inhibit the Expression of Interleukin-6 in Lipopolysaccharide-induced Human Umbilical Vein Endothelial Cells Through p38 and ERK1/2 Protein Kinases

Chitosan oligosaccharides (COS) have been reported to exert anti-fungal activities, antitumour activities and immuno-enhancing effects. However, the potential roles of COS in the treatment of vascular inflammations remain unknown. In the present study, we examined the effects of COS on interleukin-6 (IL-6) production in human umbilical vein endothelial cells (HUVECs) induced by lipopolysaccharide (LPS). Induction of HUVECs with LPS (100 ng/ml) increased the mRNA expression and protein secretion of IL-6 (versus the vehicle-treated group, p < 0.01), which were significantly reverted by the pre-treatment with COS (50-200 microg/ml) for 24 hr before LPS exposure (versus the LPS-treated group, p < 0.05 or 0.01). Signal transduction studies showed that the pre-treatment of HUVECs with COS (50-200 microg/ml) for 24 hr markedly inhibited the LPS-induced over-expression of phosphorylated p38 mitogen-activated protein kinase (MAPK), phosphorylated ERK1/2 and nuclear factor kappaB (NF-kappaB). Moreover, the LPS-induced NF-kappaB activation was suppressed by the specific ERK1/2 inhibitor PD98059 (30 microM) (versus the LPS-treated group, p < 0.01), but not by the specific p38 MAPK inhibitor SB203580 (25 microM). Additionally, both MAPK inhibitors markedly suppressed LPS-induced IL-6 mRNA expression in HUVECs (versus the LPS-treated group, p < 0.01). In conclusion, our results suggest that COS inhibit LPS-induced up-regulation of IL-6 in HUVECs, and this can be regulated by at least two parallel signalling pathways: one via p38 MAPK pathway independent of NF-kappaB activation and one via ERK1/2 pathway dependent on NF-kappaB activation.

The impact of MIG1 and/or MIG2 disruption on aerobic metabolism of succinate dehydrogenase negative Saccharomyces cerevisiae

The zinc finger proteins Mig1 and Mig2 play important roles in glucose repression of Saccharomyces cerevisiae. To investigate whether the alleviation of glucose effect would result in an increase in aerobic succinate production, MIG1 and/or MIG2 were disrupted in a succinate dehydrogenase (SDH)-negative S. cerevisiae strain. Moreover, their impacts on physiology of the SDH-negative S. cerevisiae strain were studied under fully aerobic conditions when glucose was the sole carbon source. Our results showed that the succinate production for the SDH-negative S. cerevisiae was very low even under fully aerobic conditions. Furthermore, deletion of MIG1 and/or MIG2 did not result in an increase in succinate production in the SDH-negative S. cerevisiae strain. However, the synthesis of acetate was significantly affected by MIG1 deletion or in combination with MIG2 deletion. The acetate production for the mig1/mig2 double mutant BS2M was reduced by 69.72% compared to the parent strain B2S. In addition, the amount of ethanol produced by BS2M was slightly decreased. With the mig2 mutant BSM2, the concentrations of pyruvate and glycerol were increased by 26.23% and 15.28%, respectively, compared to the parent strain B2S.