No abstract

Aspergillus oryzae aminohydrolase free acid phosphodiesterase catalyzes nicotinamide adenine dinucleotide to deamino-NAD and ammonia. The enzyme was purified to homogeneity by a combination of acetone precipitation, anion exchange chromatography and gel filtration chromatography. The enzyme was purified 230.5 fold. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme showed a single protein band of MW 94 kDa. The enzyme displayed maximum activity at pH 5 and 40 °C with NAD as substrate. The enzyme activity appeared to be stable up to 40 °C. The enzyme activity was enhanced slightly by addition of Na⁺ and K⁺, whereas inhibited strongly by addition of Ag⁺, Mn²⁺, Hg²⁺ and Cu²⁺ to the reaction mixtures. The enzyme hydrolyzes several substrates, suggesting a probable non-specific nature. The enzyme catalyzes the hydrolytic cleavage of amino group of NAD, adenosine, AMP, CMP, GMP, adenosine, cytidine and cytosine to the corresponding nucleotides, nucleosides or bases and ammonia. The substrate concentration-activity relationship is the hyperbolic type and the apparent Km and Kcat for the tested substrates were calculated.

No abstract

Cell-free extracts of nitrate-grown Penicillium politans NRC-510 could catalyze the hydrolytic deamination of adenosine to inosine maximally at pH 6.0 and 45 degrees C. However the same extracts could not catalyze the N-glycosidic bond cleavage of adenosine at pH 4.0, 6.0 and 8.0. Incubation of the extracts at 55 degrees C for 30 minutes caused about 31% loss in activity whereas incubation of the extracts at 60 degrees C for 15 minutes caused a complete loss of enzyme activity. Results indicated the absence of the involvement of sulfhydryl groups in the catalytic site of adenosine deaminase. The enzyme is inhibited by ethylene diamine tetraacetate indicating that adenosine deaminase is a metalloenzyme. MnCl2 and MgCl2 had a remarkable activating effect, whereas HgCl2, CaCl2 and ZnSO4 showed an inhibitory effect on enzyme activity. Dialyzing the extracts for 24 hours significantly increase deaminase activity by about 33%. The apparent K(m) value was calculated for adenosine and found to be 3.63 x 10(-3) M, which indicates high affinity of adenosine deaminase for its substrate adenosine.

a-Galactosidase (E.C.3.2.1.22) from Penicillium janthinellum was purified by precipitation and fractionation with ammonium sulphate, cold acetone or ethanol, calcium phosphate gel, and column chromatographies on Sephadex G-100 and G-200: The enzyme was purified about 110.39-fold when Sephadex G-100 was used. a-Galactosidase exhibited the optimum pH and temperature at 4.5 and 60 "C, respectively. The optimum enzyme stability was obtained at pH 3.5 for 24 h (at room temperature). The enzyme was found to be thermostable below 65°C up to 40minutes and was gradually inactivated by increasing the temperature above this degree. The MICHAELS constant was 0.55 mM for p-nitrophenyl-a-D-galactoside. The a-galactosidase activity was strongly inhibited by Hg' + and slightly activated by M n + + . The results show the possibility of producing a thermostable enzyme from a low-priced agricultural product, for instance, lupine.