Shiau Rong-Jen, Wen Yu-Der, Jeang Chii-Ling
Department of Beauty Science, Chienkuo Technology University, Changhua 500, Taiwan.
Arch Microbiol. 2008 Dec;190(6):651-5. doi: 10.1007/s00203-008-0417-z. Epub 2008 Aug 15.
Raw starch-digesting amylases (RSDAs) in many microorganisms convert starch granules into maltodextrins and simple sugars. We cloned and sequenced from Cytophaga sp. an RSDA with an excellent raw starch digestion activity. This RSDA was highly inducible by raw starch, but not by other sugars, suggesting that an unknown signal transduction mechanism is involved in the degradation of raw starch. We used a proteomic approach to investigate the effect of raw starch on protein expression in Cytophaga sp. Using MALDI-TOF MS protein analysis, we have identified three proteins up-regulated by raw starch, i.e., a 60-kDa chaperonin (cpn60), glutaminase, and pyruvate phosphate dikinase (PPDK). Subsequent time-course studies detected an increased expression of RSDA as well as the highest expression of PPDK occurring 6 h post-incubation with raw corn starch, implying that the latter enzyme may work along with RSDA on the digestion of raw starch. Finding these proteins up-regulated by raw starch may provide an insight into how Cytophaga sp. cells respond to raw starch stimulation.
许多微生物中的生淀粉消化淀粉酶（RSDAs）可将淀粉颗粒转化为麦芽糊精和单糖。我们从噬纤维菌属（Cytophaga sp.）中克隆并测序了一种具有出色生淀粉消化活性的RSDA。这种RSDA受生淀粉高度诱导，但不受其他糖类诱导，这表明一种未知的信号转导机制参与了生淀粉的降解过程。我们采用蛋白质组学方法来研究生淀粉对噬纤维菌属蛋白质表达的影响。通过基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）蛋白质分析，我们鉴定出三种受生淀粉上调表达的蛋白质，即一种60 kDa的伴侣蛋白（cpn60）、谷氨酰胺酶和丙酮酸磷酸双激酶（PPDK）。随后的时间进程研究检测到RSDA的表达增加，以及在与生玉米淀粉孵育6小时后PPDK的表达达到最高，这意味着后一种酶可能与RSDA一起参与生淀粉的消化。发现这些受生淀粉上调表达的蛋白质可能有助于深入了解噬纤维菌属细胞如何响应生淀粉刺激。
