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红曲霉葡萄糖淀粉酶(EC3.2.1.3)在凝胶电泳上呈现3—5个极为接近均具有酶活性的区带,测定了其中主要的两个分子型E_3和E_4的紫外吸收特性,它们在水,pH5.0醋酸缓冲液,pH7.0柠檬酸缓冲液中吸收光谱十分接近,吸收峰均在280nm。E_3在水溶液中280nm时δ=11.3×10~4,A_(1cm)~(1%)=20.4,E_4在水溶液中280nm时ε=11.0×10~4 A_(1cm)~(1%)=20.0,E_3和E_4在0.1N NaOH中吸收均增强且峰位红移,在0.1N HCI中吸收峰略为蓝移。测定了E_3和E_4在pH3.1和pH3.6时的温度差光谱,在pH3.1 E_3和E_4 △A变化极小,在pH3.6,E_3比E_4 △A变化大,但转变温度E_3和E_4都在56℃左右。E_3和E_4酪氨酸光谱滴定行为极为接近,其pK值在11.5左右。测定了E_3pH差光谱和变性差光谱,以pH2.66为参比溶液,在pH3.55、4.65、7.14及7.84可以见到酪氨酸和色氨酸的差吸收峰。8M尿素和6M盐酸胍均能使E_3出现酪氨酸和色氨酸的负的差吸收峰。
Monascus glucoamylase (EC 3.2.1.3) showed three to five bands with very close enzymatic activity on gel electrophoresis, and the UV absorption characteristics of the two main molecular types E_3 and E_4 were determined. They were In water, pH5.0 acetate buffer, pH7.0 citrate buffer absorption spectrum is very close, the absorption peak at 280nm. E_3 is 11.3 × 10 ~ 4 and A_ (1cm) ~ (1%) = 20.4 at 280nm in aqueous solution, and ε = 11.0 × 10 ~ 4 A_ (1cm) ~ (1%) = 20.0 The absorption of E_3 and E_4 in 0.1N NaOH increased and the peak position shifted red. The absorption peak shifted slightly in 0.1N HCI. The temperature difference spectra of E_3 and E_4 at pH3.1 and pH3.6 were measured. The changes of E_3 and E_4ΔA at pH3.1 were very small. At pH3.6, the changes of E_3 and E_4ΔA were larger than those at E3 and E3 E_4 are about 56 ℃. E_3 and E_4 tyrosine spectral titration behavior is very close, the pK value of about 11.5. The difference spectrum of E_3pH and the spectrum of denaturation were determined. The differential absorption peak between tyrosine and tryptophan was found at pH 3.56, pH 4.65, pH 7.45 and pH 7.85. Both 8M urea and 6M guanidine hydrochloride caused E_3 to have negative absorption peaks of tyrosine and tryptophan.