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Biomedical subjects

You-Shang Zhang

Publications and source records attributed to You-Shang Zhang.

6 recordsLinked to original sources
PubMed2004

Synthesis and characteristics of an aspartame analogue, L-asparaginyl L-3-phenyllactic acid methyl ester.

An aspartame analogue, L-asparaginyl L-3-phenyllactic acid methyl ester was synthesized with aspartic acid replaced by asparagine and peptide bond replaced by ester bond. The aspartic acid of aspartame could be replaced by asparagine as reported in the literature. In this analogue, the hydrogen of amide group could still form a hydrogen bond with the oxygen of ester bond and the ester bond was isosteric with peptide bond. However, the product was not sweet, showing that the peptide bond could not be replaced by ester bond. The peptide C-N bond behaves as a double bond that is not free to rotate and the C, O, N and H atoms are in the same plane. The replacement of peptide bond by ester bond destroyed the unique conformation of peptide bond, resulting in the loss of sweet taste.

Aspartame↗
PubMed2003

Monomeric B27 Lys destripeptide insulin: semisynthesis, characterization and biological activity.

In this paper, we report the semisynthesis of B27 Lys destripeptide insulin (B27 Lys DTrI), i.e. destetrapeptide insulin with an additional Lys residue at the C-terminus of B-chain. B27 Lys DTrI is also monomeric as shown by gel filtration. Its in vivo biological activity is 80% in comparison with that of native insulin. The addition of a Lys residue at the C-terminus of B-chain makes it possible to obtain monomeric B27 Lys DTrI from a precursor expressed in Saccharomyces cerevesiae by tryptic hydrolysis instead of the less efficient tryptic transpeptidation.

Amino Acid Sequence↗
PubMed1999

Secretory Expression of Human Insulin in Methylotrophic Yeast Pichia pastoris.

The porcine insulin precursor (PIP) gene and its derivative form sp-PIP gene, which had a nona-peptide (called spacer peptide, sp) added at the 5' terminus of PIP gene, were inserted into the plasmid pPIC9 of Pichia pastoris to obtain secretory plasmid pPIC9/PIP and pPIC9/sp-PIP, respectively. P.pastoris GS115 was transformed by pPIC9/PIP or pPIC9/sp-PIP and the high-copy strains, P39(-sp) and S51(+sp), were selected by dot-blotting. The expression levels of PIP and sp-PIP were 10 mg/L and 40 mg/L in 1 L shake flask, respectively, indicating that the spacer peptide could increase the expression. The expression level of PIP (sp-PIP) in P.pastoris was higher than that of PIP in S.cerevisiae and K.lactis reported in this laboratory. The expression level of sp-PIP was 250 mg/L in 10 L fermentor. Recombinant human insulin was obtained by means of transpeptidation of PIP or sp-PIP. The receptor binding capacity is identical with that of porcine insulin. In vivo biological activity of the recombinant human insulin is 27 IU/mg.

Journal Article↗
PubMed1997

The Transferrins from Amphioxus and the Molecular Evolution of Transferrin.

An amphioxus transferring was isolated and purified from the Xiamen amphioxus. Its physio-chemical properties are the same as those of Qingdao amphioxus transferrin. It is a glyco-protein with a molecular weight of 26 kD that is about a quarter of that of the transferrin from vertebrates. Its partial amino acid sequence and its C-terminal fragment were determined. By comparison with the sequence of human serum transferrin, it has been found that the sequence of human serum transferrin can be divided into 4 fragments with about equal size as the sequences of the amphioxus transferrin. There is quite a high homology between the sequences of amphioxus transferrin and each of the 4 fragments as well as between the four fragments. The results demonstrate that the current transferrin may be evolved from an ancestor transferrin with one quarter of the molecular weight as a result of twice gene duplication. Amphioxus transferrin may be the representative from of such ancestor transferrin.

Journal Article↗
PubMed1997

Secretory Expression of Porcine Insulin Precursor in Kluyveromyces lactis and Its Conversion into Human Insulin.

Porcine insulin precursor (PIP) was cloned to vectors derived from plasmid pKD1 and expressed in Kluyveromyces lactis. The secretory expression level of PIP was 20 to 30 mg per liter of the culture medium. Human insulin obtained from PIP through tryptic transpeptidation was characterized. Its amino acid composition, crystalline shape and biological activity are identical with those of native insulin.

Journal Article↗