| Titles |
|
English :
|
Biochemical studies of lactate dehydrogenase enzyme and vitamin B2 related to milk and dairy by- product.
|
|
Arabic :
|
دراسات كيمائية حيوية على انزيم اللاكتات دي هيدروجيناز و فيتامين ب2 و علاقتهما باللبن و المنتجات الثانوية.
|
|
| Abstract |
Milk is one of the most important body fluid in all mammals. The
most important biochemical food industries is cheese manufacture. After the action of rennin as milk clotting enzyme; whey was obtained which consider as a good source of vitamins and enzymes especially Vito B2 and lactate dehydrogenase.
Riboflavin (Vit.B2'' C17 H2O N4 °6'' Mol.Wt.376.36 ) is greenish yellow substance present in all body fluid especially blood and milk which playa significant biochemical function. FMN and FAD are coenzymes of flavin dependant enzymes which have a fundamental role in biochemical system (Dixon and webb, 1979).
Flavin have the chracteristic yellow colour resulting from strong absorption in violet and blue regions. The spectra of riboflavin and FMN are almost identical and have 3 peaks at 266, 373, and 445 nm as shown in Fig. (12) ; (Yagi, 1962).
The experimental results of Vit. B2 can be summarized as follow:
1- Riboflavin (Vit. B2) was separated from cheese whey and purified by column chromatographic methods (Fig.7a, 7b).
2- The whey sample was passed through the resin column to adsorb
the riboflavin, and the eluted fractions were detected spectro-photometrically at 445 nm (Fig.8).
3- The eluted fractions which gave the maximum absorbance at 445 nm
were pooled and performed for purification on sephadex G15 column (Fig.7b).
4- After separation and purification of riboflavin by resin and sephadex G15 column; the absorption spectra of eluted fractions were plotted (Fig.11) and compared with spectrum of standard riboflavin (Fig.s).
5- The melting point, the elements analysis and the molecular weight determination of the purified sample confirmed the presence of riboflavin.
6- from the experimental data we concluded that resin and sephadex
G15 column chromatographic analysis was more effective for fractionation and identification of riboflavin by chemical and physicochemical methods.
The experimental results of whey LDH can be summarized as follow:
1- Lactate dehydrogenase (LDH) is an oligomeric enzyme has mol. wt.
of 140 000 (LDH; L-Lactate: NAD oxidoreductase, EC 1.1.1.27)
catalyzed the chemical reaction:
t Sod. pyruvate + NADH + H LDH Lactate + NAD+
The rates of reaction in either direction are conveniently measured spectrophotometrically by the appearance or disappearance of the reduced coenzyme since it has a characteristic ultraviolet absorbance at 340 nm.
2- LDH activities of cheese whey was investigated and analysed. The effect of enzyme concentration (Fig.13) was studied; a linear relationship between LDH velocity and enzyme concentration in the rang used (0.05 - 0.3 ml''s taken of whey).
The velocity expressed as A at 340 nm proportion to the LDH concentration.
3- When velocity of LDH was plotted against sod. pyruvate concentration ranged from 0.5 - 18 mmol, a section of rectangular hyberbola was obtained (Fig. 16).
4- The optimum PH was found to be 7.4 (Fig. 17) such PH curve for
LDH, it will be seen that the fall in the alkaline side is most probably due to some conformational changes occur in the oligomerization of LDH.
5- The spectrum of standard NADH was measured spectrophoto- metrically from 200 - 500 nm ; two bands can be observed at 260
and 340 nm as reported in literature data (Fig. 2). The reduction of pyruvate to lactate can be detected spectrophoto-metrically by conversion of NADH to NAD+With gradually quenching of the band at 340 nm (Fig. 19,20,21).
6- Experimentally the rate of quenching of the band at 340 nm due to the enzymatic reaction of LDH with sod. pyruvate differ from the source of the enzyme LDH. Fig.(22) shows the rate of quenching of NADH band at 340 nm during the enzymatic reaction of different types of LDH as function of time.
|
| Publication year |
1993
|
| Availability location |
مكتبة معهد بحوث الانتاج الحيوانى- شارع نادى الصيد - الدقى - الجيزة
|
| Availability number |
450
|
| Organization Name |
Animal Production Research Institute (APRI)
|
| Country |
Egypt
|
| Department |
Dairy Chemistry Research Department
|
| Author(s) from ARC |
|
| Agris Categories |
Animal physiology and biochemistry
|
AGROVOC
TERMS |
Cheesemaking.
Chemistry.
Enzymes.
Milk byproducts.
|
| Publication Type |
Master Thesis
|