- Transmucosal delivery of methionine enkephalin. I: Solution stability and kinetics of degradation in various rabbit mucosa extracts
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To evaluate the feasibility of transmucosal delivery of methionine enkephalin (Tyr-Gly-Gly-Phe-Met; Met-Enk), it is important to first investigate its physicochemical and enzymatic stability. The kinetics of degradation of Met-Enk in aqueous solution was determined at pH 2.01-9.84 and 37-45 °C by high-performance liquid chromatography. The first-order rate constant (k) was calculated, and the log k-pH profile showed that Met-Enk is most stable at pH ~5.0. Various mucosae excised from rabbit were mounted on Valia-Chien permeation cells and exposed to isotonic phosphate buffer at physiologic pHs. Mucosal and serosal extracts were collected from the donor and receptor solutions, respectively. The degradation of Met-Enk in the extracts followed first-order kinetics, but no significant difference in the degradation rates was observed between mucosal and serosal extracts, regardless of the type of mucosa used. Degradation was most rapid in the extracts of rectal mucosa, followed by vaginal and nasal mucosae. The major metabolites were Des-Tyr-Met-Enk and Tyrosine (Tyr), indicating the enzymatic hydrolysis by aminopeptidases. However, the data also suggested that dipeptidyl peptidase and dipeptidyl carboxypeptidase could play some roles in the degradation of Met-Enk. The degradation pathways of Met-Enk were further explored by concomitantly determining the formation of smaller metabolites of primary hydrolytic fragments of Met-Enk in the mucosal extracts.
- In Koo Chun,Chien
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- γ-Valerolactone (GVL): An eco-friendly anchoring solvent for solid-phase peptide synthesis
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Due to the hazardous nature of CH2Cl2, regulatory authorities have imposed restrictions to minimize or even stop its use. It has therefore become imperative to identify environmentally benign solvents to replace it. Here we report on a bio derived solvent, γ-valerolactone, for the incorporation of the first amino acid onto p-alkoxybenzyl alcohol resin in solid-phase peptide synthesis. Satisfactory loading values (by a spectrophotometric method) were achieved. Furthermore, racemization and dipeptide formation were also checked and found to be acceptable.
- Al Musaimi, Othman,El-Faham, Ayman,Basso, Alessandra,de la Torre, Beatriz G.,Albericio, Fernando
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- Peptide bond formation by aminolysin-A catalysis: A simple approach to enzymatic synthesis of diverse short oligopeptides and biologically active puromycins
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A new S9 family aminopeptidase derived from the actinobacterial thermophile Acidothermus cellulolyticus was cloned and engineered into a transaminopeptidase by site-directed mutagenesis of catalytic Ser491 into Cys. The engineered biocatalyst, designated aminolysin-A, can catalyze the formation of peptide bonds to give linear homo-oligopeptides, hetero-dipeptides, and cyclic dipeptides using cost-effective substrates in a one-pot reaction. Aminolysin-A can recognize several C-terminal-modified amino acids, including the l- and d-forms, as acyl donors as well as free amines, including amino acids and puromycin aminonucleoside, as acyl acceptors. The absence of amino acid esters prevents the formation of peptides; therefore, the reaction mechanism involves aminolysis and not a reverse reaction of hydrolysis. The aminolysin system will be a beneficial tool for the preparation of structurally diverse peptide mimetics by a simple approach.
- Usuki, Hirokazu,Yamamoto, Yukihiro,Arima, Jiro,Iwabuchi, Masaki,Miyoshi, Shozo,Nitoda, Teruhiko,Hatanaka, Tadashi
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p. 2327 - 2335
(2011/05/02)
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- Engineered transaminopeptidase, aminolysin-S for catalysis of peptide bond formation to give linear and cyclic dipeptides by one-pot reaction
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Aminopeptidase from Streptomyces thermocyaneoviolaceus NBRC14271 was engineered into transaminopeptidase and used to catalyze an aminolysis reaction to give linear and cyclic dipeptides from cost-effective substrates such as the ester derivatives of amino
- Usuki, Hirokazu,Uesugi, Yoshiko,Arima, Jiro,Yamamoto, Yukihiro,Iwabuchi, Masaki,Hatanaka, Tadashi
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supporting information; experimental part
p. 580 - 582
(2010/05/01)
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