Insulin precursor fusion protein expressed in Pichia pastoris is a single-chain protein with a spacer peptide (EEAEAEAEPK) localized at its N-terminal. Currently, the one-step transpeptidation reaction with low yield and high cost is generally employed to convert the insulin precursor fusion protein into human insulin ester. In this study, a two-step transpeptidation reaction was proposed separating the cleavage step from the coupling step so that each reaction was performed under its optimal conditions. Using this method, the total efficiency doubled and the reaction time was shortened compared with the one-step method. In addition, the amount of O-t-butyl-l-threonine t-butyl ester and trypsin dosages were reduced by 50% and 75%, respectively. This two-step transpeptidation strategy was simple and efficient and could be used for the pharmaceutical production of human insulin.
Colla corii asini hydrolysates (ACCH) and ginkgo biloba extracts (EGb) possess more potent antioxidant effects when used in combination than when used alone. The mixture of ACCH and EGb at a dose ratio of 20:4(w:w) showed the highest radical scavenging activity with IC
50 of 0.17 ± 0.01, 0.43 ± 0.02 and 1.52 ± 0.07 mg/ml against DPPH, ABTS and HO
· free radicals, respectively. Furthermore, the inhibition of breast cancer cells MCF‐7 and MDA‐MB‐231 proliferation increased when these cell lines were treated with a combination of ACCH and EGb for 72 hr, with IC
50 of 4.32 ± 0.12 mg/ml and 0.39 ± 0.01 mg/ml, respectively. The findings indicated that the mixtures of ACCH and EGb could be used to prevent and treat some diseases caused by the excessive free radicals, especially cancer. Therefore, the mixtures of ACCH and EGb might serve as a natural source of desirable antioxidant and anticancer agents for the nutraceutical and pharmaceutical industries.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.