Purification and molecular properties of an alpha-galactosidase synthesized and secreted by Aspergillus nidulans.
alpha-Galactosidases from mycelial extract and culture filtrate of Aspergillus nidulans have been purified to homogeneity and utilised to obtain polyclonal antibodies anti-alpha-galactosidase. The enzymatic characteristics and the cross reactivity of the antibodies suggest that alpha-galactosidases isolated from the two sources were the same enzyme. Thus, A. nidulans synthesized and secreted only one enzymatic form of alpha-galactosidase which is a multimeric enzyme of 370 kDa composed of four monomers of 87 kDa and a pI of 6.3. The optimum temperature of activity was 50 degrees C and the optimum pH 4-5. The enzyme was stable over a wide range of pH but quite unstable to temperature. alpha-Galactosidase of A. nidulans is a very specific enzyme, it is active only on p-nitrophenyl-alpha-D-galactoside (PNPG), melibiose and raffinose. When PNPG was utilised as substrate melibiose, raffinose, galactose and glucose were competitive inhibitors of the activity.
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Departamento de Microbiología y Parasitología, Universidad de Alcalá de Henares, Madrid, Spain.
Pedregosa
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AM
Fernández Monistrol
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Laborda
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D001233:Aspergillus nidulans / Q000201:enzymology*; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007120:Immunochemistry; D008970:Molecular Weight; D011487:Protein Conformation; D013696:Temperature; D000519:alpha-Galactosidase / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification*
D000519:alpha-Galactosidase