Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of the insulin and leptin receptor pathways and thus an attractive therapeutic target for diabetes and obesity. Starting with a high micromolar lead compound, structure-based optimization of novel PTP1B inhibitors by extension of the molecule from the enzyme active site into the second phosphotyrosine binding site is described. Medicinal chemistry, guided by X-ray complex structure and molecular modeling, has yielded low nanomolar PTP1B inhibitors in an efficient manner. Compounds from this chemical series were found to be actively transported into hepatocytes. This active uptake into target tissues could be one of the possible avenues to overcome the poor membrane permeability of PTP1B inhibitors.
An analytical method was developed for determining free and oligosaccharide-bound sialic acids in bovine colostrum by HPLC. The condition of acid hydrolysis for sample and sialic acids derivatization were investigated. The sialic acids were released from their parent oligosaccharides by acid hydrolysis using 40mL 0.1mol/L sulphuric acid for 100min. They were then derivatized using O-phenylenediamine (OPD) at 70°C for 40 min, the determination of the derivative could be carried out by UV detection. The total content of free and oligosaccharide bound sialic acids in bovine colostrum milk were 941.95μg/mL. The developed method is validated on various dairy products such as bovine milk and milk-based products.
Galactose is found in many oligosaccharides, galactomannans, glycoproteins and glycolipids, which are widely distributed in plants microorganisms and animals. α-Galactosidase (α-Gal) catalyzes the hydrolysis of 1,6-linked α-galactosyl residues and transgalactosylation. α-Gals are classified into four glycoside hydrolases families (GH): 4, 27, 36 and 57. The majority of known α-Gals belongs to GH families 27 and 36.α-Gals are of particular interest in view of their biotechnological applications.
The present study studied the effect of chitosan coating with antibrowning agents, including naphthylacetate and cinnamon oil, and modified atmosphere packaging (MAP) on browning of sweet persimmons stored at - 0.3 ~ 0 °C for 3 months. The browning on the surface of sweet persimmons was effectively inhibited by chitosan - based coating and MAP treatment. After 3 months’ storage, samples coated + MAP exerted the lowest browning index(BI), polyphenol oxidase (PPO) activity and malondialdehyde (MDA) content, which indicated that the coated + MAP treatment could offer an excellent inhibitory effect on the browning. Both edible coating and MAP treatment cause changes in respiration rate of sweet persimmons. This research could be valuable for the development of application to edible coating and MAP for improving the shelf - life properties of sweet persimmons.
The basic study on activity of polyphenol oxidase (PPO) from purple sweet potato (PSP) and its control method was mainly carried out by spectrophotometry. The PPO activity and browning degree (BD) of PSP peel were higher than those of inner-tissue and intact sweet potatoes. The relativity between them was positive, and relativity coefficient was 0.9895. The activity of PPO extracted from sliced PSP increased initially and decreased afterwards, with the highest activity of PPO on the third day during storage. And BD increased very quickly as time went by, especially in the first three days. The relativity between PPO activity and BD was negative, and relativity coefficient was-0.8747. The result indicated that the browning of fresh-cut PSP slices during storage was mainly due to PPO in it. The composite inhibitor was optimized by the orthogonal design, and the addition of0.05% L-cysteine+0.03% phytic acid+0.3% ascorbic acid+0.3% citric acidwould markedly inhibit the enzymatic browning caused by PPO and improve the quality of fresh-cut PSP slices.
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