Maltotriitol inhibition of maltose metabolism in Streptococcus mutans via maltose transport, amylomaltase and phospho-alpha-glucosidase activities.
Maltotriitol inhibition of maltose metabolism in Streptococcus mutans via maltose transport, amylomaltase and phospho-alpha-glucosidase activities.
复制标题
麦芽三醇通过麦芽糖转运、麦芽糖淀粉酶和磷酸-α-葡萄糖苷酶活性抑制变形链球菌中的麦芽糖代谢。
作者：
P. Würsch;B. Koellreutter
麦芽三醇(MTL)能抑制变形链球菌OMZ 176中麦芽糖的糖酵解和转运。糖醇被摄取了，但没有被代谢。生长在葡萄糖和麦芽糖上的细胞存在磷酸烯醇式丙酮酸：麦芽糖磷酸转移酶(PEP：PTS)系统的活性，且不受MTL的抑制。麦芽糖PTS反应产物经分离鉴定为麦芽糖6‘-磷酸。麦芽糖诱导的磷酸-α-葡萄糖苷酶将磷酸麦芽糖分解为葡萄糖和6-磷酸葡萄糖。纯化了催化葡萄糖和麦芽糊精单位转移的麦芽糖诱导的淀粉酶。麦芽糖的表观Km值为21.8 mm。MTL对麦芽糖(KI 2.0 mM)和麦芽三糖的酶活性有抑制作用，但以麦芽七糖为底物时，MTL发生转糖基化反应。这些结果表明，在OMZ176菌株中，麦芽糖的运输是由依赖于PEP的麦芽糖PTS产生麦芽糖6‘-磷酸，该麦芽糖被麦芽糖诱导的磷酸-α-葡萄糖苷酶降解。提示MTL通过降低麦芽糖转运速率，抑制淀粉酶和磷酸α葡萄糖苷酶活性，导致麦芽糖6‘-磷酸积聚，从而抑制麦芽糖的糖酵解。
Maltose glycolysis and transport in Streptococcus mutans OMZ 176 were shown to be inhibited by maltotriitol (MTL). The sugar alcohol was taken up, but was not metabolized. The phosphoenolpyruvate: maltose phosphotransferase (PEP:PTS) system activity was present in cells grown on glucose and maltose and was not inhibited by MTL. The product of the maltose PTS reaction was isolated and identified as maltose 6′-phosphate. The phospho-α-glucosidase induced by maltose hydrolyzed maltose phosphate into glucose and glucose 6-phosphate. The maltose-inducible amylomaltase which catalyses the transfer of both glucosyl and maltodextrinyl units was purified. The apparent Km for maltose was 21.8 mM. MTL inhibited the enzyme activity on maltose (Ki 2.0 mM) and maltotriose without being itself a substrate, but transglycosylation occurred on MTL when maltoheptaose was the donor substrate. These results indicated that in strain OMZ 176, maltose transport was mediated by a PEP-dependent maltose PTS yielding maltose 6′-phosphate which subsequently was hydrolyzed by a maltose-inducible phospho-α-glucosidase. It was suggested that MTL inhibits glycolysis of maltose by reducing the rate of maltose transport and inhibiting amylomaltase and phospho-α-glucosidase activities, resulting in an accumulation of maltose 6′-phosphate.