Phenolics, phytic acid, and phytase in Canadian-grown low-tannin faba bean (Vicia faba L.) genotypes

Purification of diamine oxidase and its properties in germinated fava bean (Vicia faba L.)

BACKGROUND

γ-Aminobutyric acid (GABA) is a non-protein amino acid with bioactive functions for human health. Diamine oxidase (DAO, EC 1.4.3.6) is one of the key enzymes for GABA formation. In the present study, this enzyme was purified from 5 day germinated fava bean and its properties were investigated in vitro.

RESULTS

The molecular mass of the enzyme estimated by Sephadex G-100 gel filtration was 121 kDa. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) displayed a single band at a molecular mass of 52 kDa. The enzyme had optimal activity at 40 °C and retained its activity after being incubated at 30 °C for 30 min. It showed higher activity at pH 6.5 than at other pH values. The enzyme was significantly inhibited by Mg(2+), Cu(2+), Fe(3+), aminoguanidine, ethylene glycol tetraacetic acid (EGTA), ethylene diamine tetraacetic acid disodium salt (EDTA-Na(2)), L-cysteine and β-mercaptoethanol. The K(m) value of DAO was 0.23 mmol L(-1) for putrescine and 0.96 mmol L(-1) for spermidine. However, the enzyme did not degrade spermine.

CONCLUSION

DAO from germinated fava bean was purified. The optimal reaction temperature and pH of the enzyme were mild. The enzyme had higher affinity to putrescine than to spermidine and spermine.

Ileal digestibility of amino acids for zero-tannin faba bean (Vicia faba L.) fed to broiler chicks

An experiment was conducted to determine the apparent ileal digestibility (AID) of amino acids (AA) in zero-tannin faba beans (ZFB; Vicia faba L.) fed to broiler chicks. In total, 120 broiler chicks were divided into 24 groups of 5 birds that were balanced for BW and fed 1 of 3 diets in a completely randomized design (8 groups/diet) from d 14 to 21 of age. The diets were a soybean meal-cornstarch-based basal diet or the basal diet with soybean meal and cornstarch replaced by 50% of either conventional (tannin-containing) faba beans (CFB) or ZFB. The CFB were fed for comparison with ZFB. All of the 3 diets contained chromic oxide (0.3%) as an indigestible marker, and nutrient digestibilities were determined by the difference method. On d 21, the birds were killed by cervical dislocation and contents of the lower-half of the ileum were obtained for determination of apparent AA digestibility. The CFB and ZFB were similar in CP, AA, neutral detergent fiber, and acid detergent fiber contents. The ZFB did not contain tannins, whereas the CFB contained 0.82% tannins. The ZFB had greater (P < 0.05) AID for all AA (except Met) compared with that of the CFB by an average of 12.6 percentage points. The 2 faba-bean types were similar in AID of Met. The results show that the ZFB evaluated in the current study had greater AID of AA than CFB, and hence, it may be a better source of protein for broiler chicks than CFB.

Factors influencing diamine oxidase activity and γ-aminobutyric acid content of fava bean (Vicia faba L.) during germination

Factors (germination time, spectra, temperature, pH, and chemical inhibitors) influencing diamine oxidase (DAO, EC 1.4.3.6) activity and γ-aminobutyric acid (GABA) content of fava bean (Vicia faba L.) during germination were investigated in this study. DAO activity significantly increased in germinating seeds but varied with different organs. The enzyme activity was higher in shoot than that in cotyledon, hypocotyl, and radicle. When seeds were germinated in the dark, DAO activity was 2.35-, 2.00-, 2.36-, 4.40-, and 1.67-fold of that under white, red, blue, green, and yellow spectra, respectively. The optimum germination temperature and pH value for increasing DAO activity were 30 °C and 3.0, respectively. The DAO activity was inhibited significantly by aminoguanidine and sodium ethylenediamine tetracetate, while it was activated by CuCl(2) and CaCl(2). Germinating at an appropriate temperature and pH, 30% of GABA formation was supplied by DAO. Calcium was related to the regulation of DAO activity and GABA accumulation.