토양으로부터 lactose의 가수분해를 촉매하는 균체외 ${eta}-galactosidase$를 생산하는 YB-9가 분리되었다. 분리균 YB-9는 분리균의 배양, 형태, 생리적 특성을 조사한 결과 Streptomyces속 균주로 동정되었다. 분리균의 배양상등액을 ammonium $sulfate(15{sim}70%)$로 처리하고 투석하여 부분정제된 ${eta}-galactosidase$를 $para-nitrophenyl-{eta}-D-galactopyranoside(pNP-{eta}Gal)$와 lactose를 기질로 하여 반응특성을 분석하기 위해 조효소액으로 사용하였다. ${eta}-Galactosidase$는 pH $6.0{sim}6.5$와 $60^{circ}C$에서 최대활성을 보였다. $pNP-{eta}Gal$과 lactose에 대한 ${eta}$-galactosidase의 가수분해 활성은 galactose에 의해 감소되었다. Lactose에 대한 가수분해 활성은 glucose에 의해 미미하게 감소하였으나, glucose에 의해 $pNP-{eta}Gal$에 대한 활성은 1.3배 증가하였다. 특히, xylose에 의한 lactose의 가수분해 활성에는 영향이 없었고, $pNP-{eta}Gal$에 대한 활성은 1.6배 증가시켰다.
A strain YB-9 was isolated from soil as a producer of the extracellular ${eta}-D-galactosidase$, which catalyzes the hydrolysis of lactose. The strain YB-9 was identified as Streptomyces sp. on the basis of its cultural, morphological and physiological properties. After treating culture supematant of the isolate with ammonium sulfate $(15{sim}70%)$, the precipitated protein was used as a crude ${eta}-galactosidase$ for analyzing its reaction properties with $para-nitrophenyl-{eta}-D-galactoside$ $(pNP-{eta}Gal)$ and lactose as substrates. The {eta}-galactosidase showed its maximal activity at pH $6.0{sim}6.5$ and $60^{circ}C$. The hydrolyzing activity of ${eta}-galactosidase$ for both $pNP-{eta}Gal$ and lactose was decreased by galactose. Its hydrolyzing activity for lactose was slightly decreased by glucose, but the activity for $pNP-{eta}Gal$ was increased to 1.3-folds by glucose. Especially, its hydrolyzing activity was not affected for lactose and was increased to 1.6-folds for $pNP-{eta}Gal$ by xylose.
