Biomedical subjects

M B Habibi-Najafi

Publications and source records attributed to M B Habibi-Najafi.

3 recordsLinked to original sources

PubMed1996

Bitterness in cheese: a review.

Bitterness, the necessary consequence of proteolysis, has been under investigation from different perspectives. This review attempts to give more up-to-date information on the definition of some principal aspects, the relationship between the proteolytic activity and bitter peptide accumulation in cheese, and methods of isolation and detection of bitter peptides. Further knowledge on the physicochemical properties of bitter peptides in cheese as well as in synthetic peptides and the possible control methods for bitterness are discussed. Particular interest in using some strains of lactobacilli or their enzymes as an adjunct in accelerated ripened cheese (ARC) and enzyme-modified cheese (EMC) without bitterness is also described in detail.

Amino Acid Sequence↗

PubMed1994

Purification and characterization of X-prolyl dipeptidyl peptidase from Lactobacillus casei subsp. casei LLG.

X-Prolyl dipeptidyl peptidase, which hydrolysed X-Pro-Y almost specifically, has been purified to homogeneity from crude cell-free extracts of Lactobacillus casei subsp. casei LLG using fast protein liquid chromatography equipped with preparative and analytical anion exchange columns. The enzyme was purified to 274-fold by ammonium sulphate fractionation, and by two successive ion-exchange chromatographies with a recovery of 34%. The purified enzyme appeared as a single band on both native-polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulphate (SDS)-PAGE and had a molecular mass of 79 kDa. The pH and the temperature optima by the purified enzyme were 7.0 and 50 degrees C, respectively. X-PDP was a serine-dependent enzyme, as both diisopropylfluorophosphate and phenylmethylsulphonylfluoride caused complete inhibition of the enzyme activity. The Michaelis constant (Km) and maximum reaction velocity (Vmax) values were 0.2 mM and 43 mM per milligram, respectively.

Biotechnology↗

PubMed1994

Proline-specific peptidases of Lactobacillus casei subspecies.

This paper describes the specific activities for proline iminopeptidases, x-prolyl dipeptidyl peptidase and post proline endopeptidase, from each of two subspecies of Lactobacillus casei grown in MRS broth and whey media at 37 degrees C, pH 6.0. The histochemical PAGE of soluble extracts from one subspecies (Lactobacillus casei ssp. casei LLG) indicated that the two enzyme activities were due to distinct proteins. Except for a slight increase in x-prolyl dipeptidyl peptidase activity, the activities of proline imino- and endopeptidases of cells grown in whey medium did not vary markedly from those of cells grown in MRS broth. The effect of inhibitor agents and pH on the activities of proline iminopeptidase and x-prolyl dipeptidyl peptidase were investigated. The temperature optima and storage stability under different conditions were also studied for these activities.

Amino Acid Sequence↗