Biomedical subjects

El Hassan Ajandouz

Publications and source records attributed to El Hassan Ajandouz.

3 recordsLinked to original sources

PubMed2007

Substrate and product hydrolysis specificity in family 11 glycoside hydrolases: an analysis of Penicillium funiculosum and Penicillium griseofulvum xylanases.

Two genes encoding family 11 endo-(1,4)-beta-xylanases from Penicillium griseofulvum (PgXynA) and Penicillium funiculosum (PfXynC) were heterologously expressed in Escherichia coli as glutathione S-transferase fusion proteins, and the recombinant enzymes were purified after affinity chromatography and proteolysis. PgXynA and PfXynC were identical to their native counterparts in terms of molecular mass, pI, N-terminal sequence, optimum pH, and enzymatic activity towards arabinoxylan. Further investigation of the rate and pattern of hydrolysis of PgXynA and PfXynC on wheat soluble arabinoxylan showed the predominant production of xylotriose and xylobiose as end products. The initial rate data from the hydrolysis of short xylo-oligosaccharides indicated that the catalytic efficiency increased with increasing chain length (n) of oligomer up to n = 6, suggesting that the specificity region of both Penicillium xylanases spans about six xylose units. In contrast to PfXynC, PgXynA was found insensitive to the wheat xylanase inhibitor protein XIP-I.

Endo-1,4-beta Xylanases↗

PubMed2005

A fast, sensitive method for the simultaneous determination of alpha-tocopherol and alpha-tocopheryl acetate in mixed micelles.

This report improves analytical procedures to investigate the behaviour of the two Vitamin E forms, alpha-tocopherol (Tol) and alpha-tocopheryl acetate (Tac), in model systems mimicking the intestinal medium. We describe how to prepare mixed micelles as vehicle for Tac and Tol and the HPLC method for their quantification in the micelles. Tac and Tol were extracted using ethanol-hexane-drying procedure, whereas the separation and detection were performed in methanol and by UV method, respectively. Both compounds were eluted in less than 4 min. In the range between 1.7 microM and 54 microM of Tac or Tol in the micelles, their recovery were 89% and 81%, respectively, with correlation coefficient over 0.99 and R.S.D. of less than 7.2% in all cases. Limits of detection and quantification for Tac and Tol in mixed micelles ranged between 1 microM and 2 microM and between 3 microM and 5 microM, respectively. The behaviours of Tac and Tol were quite different during the extraction procedure and both were influenced by the vitamin concentration and the relative volume of organic solvents.

Chromatography, High Pressure Liquid↗

PubMed2005

Molecular basis of the effects of chloride ion on the acid-base catalyst in the mechanism of pancreatic alpha-amylase.

Pig pancreatic alpha-amylase (PPA), an enzyme belonging to the alpha-amylase family, is involved in the degradation of starch. Like some other members of this family, PPA requires chloride to reach maximum activity levels. To further explain the mechanism of chloride activation, a crystal of wild-type PPA soaked with maltopentaose using a chloride-free buffer was analyzed by X-ray crystallography. A conspicuous reorientation of the acid/base catalyst Glu233 residue was found to occur. The structural results, along with kinetic data, show that the acid/base catalyst is maintained in the active site, in an optimum position, pointing toward the scissile bond-atom, due to the presence of chloride ions. The present study therefore explains the mechanism of PPA activation by chloride ions.

Animals↗