抄録
A strain of Zoogloea ramigera isolated from soil produced an extracellular α-amylase with unusual characteristics. The extracellular α-amylase from Z. ramigera was purified to apparent homogeneity by starch adsorption and CM-Toyopearl ion-exchange chromatography. The enzyme had an isoelectric point of 8.8 and apparent molecular mass of 63, 000 Da, as estimated by SDSPAGE. The 15-amino acid NH2 terminal sequence was different from other raw starch-digesting enzyme, α-Amylase activity on raw corn starch was optimal at pH 6.0 to 6.5. The enzyme was relatively stable between pH 5.0 and 8.0 and at temperatures below 50°C. When acted on raw corn starch, the enzyme produced maltopentaose alone in the early stage of hydrolysis. On further incubation, maltose and maltotriose were produced with concomitant decrease of maltopentaose. The COOH-terminal portion of the amylase from Z, ramigera contained several sequences significantly homologous, to those of other raw starch-digesting enzyme. In the synergism of the amylase from Z. ramigera and glucoamylase from Rhizopus niveus on hydrolysis of raw corn starch, role of the amylase was supplying of new substrate molecules for glucoamylase by endowise splitting of large molecules.
