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α - acetolactate decarboxylase exists in many bacteria , fungi , algae and protozoa had no α-acetolactate decarboxylase activity . It directly to the degradation of α-acetolactate 3 - hydroxy - butanone ( acetoin ) , to avoid generating diacetyl this step , a very important role in brewing . Derived from Bacillus subtilis ( from Bacillus subtilis ) , 3226-5 , α-acetolactate decarboxylase precipitated by ammonium sulfate fractionation , heat treatment , the DEAE-Sepharose Fast Flow ion exchange column chromatography and other separation and purification steps , to give SDS-PAEG electrophoresis pure, by N - terminal amino acid sequence analysis to verify the purity of the enzyme protein . Its enzymatic properties . α-acetolactate decarboxylase fractionally precipitated by 50 % to 80% ammonium sulfate , 50 ° C , 2min heat treatment , the DEAE-Sepharose Fast Flow ion exchange column chromatography separation and purification . In the ion exchange column chromatography , using different pH values ??and different types of buffer to optimize the purification conditions , the final choice pH6.0 MES buffer and the elution point of the enzyme protein to 0.24 ~ 0.32mol/LNaCl . α-acetolactate decarboxylase specific activity increased 15.5 times , the recovery rate was 20.3 % . Studies show that the enzyme properties single subunit of the enzyme having a molecular weight of 32kDa ; sensitive to heat ( 40 ° C or above) ; optimum pH value of 7 ; stable pH value of 7 ; to α-acetolactate as substrate , α - the acetolactate decarboxylase power parameters Km for 232.6mmol / L and Vmax of 7.1 μ mol / ( μ g.min ) ; Mg 2 , Mn 2 , Zn < sup> 2 < / sup> Fe 2 < / sup> Fe 3 , Cu 2 < / sup> divalent metal ions can activate the α-acetolactate decarboxylase activity ; join metal chelate agent EDTA , make a decreased activity of the atomic absorption spectrophotometer to the Zn 2 < / sup> ; branched chain amino acids did not affect the α-ALDC enzyme activity .
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