近日,，山東大學(xué)微生物技術(shù)國(guó)家重點(diǎn)實(shí)驗(yàn)室,、山東大學(xué)海洋生物技術(shù)研究中心張玉忠教授課題組在深海微生物學(xué)研究領(lǐng)域取得了重要進(jìn)展,，其研究成果分別于2008年12月26日,、2009年1月30日發(fā)表在國(guó)際知名雜志《生物化學(xué)雜志》（Journal of Biological Chemistry,，JBC (2008, 283 (52): 36100)）、《生物化學(xué)雜志》（Journal of Biological Chemistry, 2009, JBC published January 30, 2009 as doi:10.1074/jbc.M808421200）,；2009年2月5日在線發(fā)表在微生物學(xué)知名雜志《應(yīng)用與環(huán)境微生物學(xué)》（Applied and Environmental Microbiology ）,。
深海中的高分子量有機(jī)氮（HMWON）都是難被化學(xué)水解和生物降解的氨基化合物（amides），即蛋白質(zhì)以顆粒有機(jī)氮（PON）和溶解有機(jī)氮 （DON）的形式存在,。因此,，深海沉積物中PON和DON的降解對(duì)沉積物中有機(jī)氮的循環(huán)非常關(guān)鍵。但至今,，深海沉積物中PON和DON的降解機(jī)制未被闡明,。張玉忠教授課題組的陳秀蘭、趙國(guó)琰等人從深海適冷菌Pseudoalteromonas sp. SM9913發(fā)現(xiàn)了一種新的S8家族多結(jié)構(gòu)域絲氨酸蛋白酶,，將其命名為Deseasin MCP-01（Microbiology-SGM,，2007, 153: 2116）。進(jìn)一步研究發(fā)現(xiàn)Deseasin MCP-01對(duì)非水溶性的膠原蛋白具有很好的降解作用,，其C-端的PKD結(jié)構(gòu)域?qū)δz原蛋白具有吸附作用,，其中36位的色氨酸是其結(jié)合膠原蛋白過(guò)程中起關(guān)鍵作用的氨基酸，PKD的結(jié)合可顯著提高催化結(jié)構(gòu)域?qū)δz原蛋白的降解效率 (JBC, 2008, 283 (52): 36100),。他們還發(fā)現(xiàn),，菌株Myroides profundi D25能夠分泌一種M12家族的新型金屬蛋白酶，將其命名為Myroilysin,。該酶能夠高效降解彈性蛋白,，但僅具有微弱的膠原蛋白酶活性，然而Myroilysin卻對(duì)膠原蛋白具有顯著的膨脹作用,，提高其它膠原蛋白酶對(duì)膠原蛋白的降解效率(Appl. Environ. Microb., published ahead of print on 5 February 2009, doi:10.1128/AEM.02285-08）,。膠原蛋白和彈性蛋白在海洋動(dòng)物體內(nèi)廣泛分布且含量豐富，并且難被化學(xué)和生物降解,，推測(cè)是海洋有機(jī)氮的重要組成部分,，因此， Deseasin MCP-01和Myroilysin可能在深海沉積物中PON和DON的降解過(guò)程中發(fā)揮重要的作用,，上述研究結(jié)果為最終闡明PON和DON的降解過(guò)程與機(jī)理提供了重要的證據(jù),。
深海（除熱液口外）終年低溫，微生物胞外蛋白酶對(duì)低溫的適應(yīng)尤為重要,。適冷酶兼有低溫下高的催化活性和高溫下低的熱穩(wěn)定性雙重性質(zhì)特點(diǎn),，但適冷酶活性－柔性－穩(wěn)定性三者之間的關(guān)系，到目前并不完全清楚,。張玉忠課題組解彬彬等人,，以M4家族的新型適冷金屬蛋白酶MCP-02和E495為研究對(duì)象，并與來(lái)源于陸地細(xì)菌M4家族的中溫酶金屬蛋白酶Pseudolysin比較,。研究結(jié)果表明,，適冷酶的蛋白質(zhì)柔性和穩(wěn)定性是由相關(guān)的但并不相同的結(jié)構(gòu)因素決定，降低穩(wěn)定性并非提高柔性的前提,。穩(wěn)定性主要取決于靜態(tài)結(jié)構(gòu)中鍵（主要包括氫鍵和鹽鍵等）的（平均）數(shù)目,，鍵數(shù)目越多，穩(wěn)定性越高,；而柔性則與這些鍵的動(dòng)態(tài)持續(xù)性（鍵的穩(wěn)定性）相關(guān),，鍵的動(dòng)態(tài)持續(xù)性越低，柔性則越高,。該課題組首次提出了優(yōu)化氫鍵動(dòng)態(tài)是酶的一項(xiàng)適冷策略,，這是蛋白質(zhì)適冷進(jìn)化研究的一個(gè)新發(fā)現(xiàn)。這對(duì)于更深入理解酶的活性－柔性－穩(wěn)定性三者之間的關(guān)系,，以及蛋白質(zhì)結(jié)構(gòu)與功能之間的關(guān)系具有重要意義,。
該項(xiàng)目組的研究工作得到了國(guó)家863計(jì)劃項(xiàng)目、國(guó)家自然科學(xué)基金和中國(guó)大洋協(xié)會(huì)國(guó)際海底區(qū)域研究開發(fā)項(xiàng)目的資助,。（生物谷Bioon.com）
生物谷推薦原始出處：
Applied and Environmental Microbiology,，doi:10.1128/AEM.02285-08，Xiu-Lan Chen,，Yu-Zhong Zhang
Myroilysin, a Novel Bacterial M12 Metalloprotease with Elastinolytic Activity and Synergistic Role with Collagenase in Collagen Hydrolysis by Swelling Collagen: Implication for Its Ecological Function in Biodegradation of Deep-Sea High-Molecular-Weight Organic Nitrogen
Xiu-Lan Chen, Bin-Bin Xie, Fei Bian, Guo-Yan Zhao, Hui-Lin Zhao, Hai-Lun He, Bai-Cheng Zhou, and Yu-Zhong Zhang*
State Key Lab of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Jinan 250100, P. R. China
Nearly all high-molecular-weight (HMW) dissolved organic nitrogen (DON) and part of the particulate organic nitrogen (PON) in deep sea are present in hydrolysis-resistant amides, and to date, their biodegradation mechanisms have yet to be resolved. M12 is the second large family in subclan MA(M) of Zn-containing metalloproteases, including most members from animals and only one (flavastacin) reported from a human pathogenic bacterium Flavobacterium meningosepticum. Here, we characterized a novel M12 protease myroilysin with elastinolytic activity and collagen-swelling ability from newly described deep-sea bacterium Myroides profundi D25. Myroilysin is a monomer enzyme with 205 amino acid residues and a molecular mass of 22936 Da. It has the same conserved residues at the four zinc ligands as astacin and very low identity (40%) to other metalloproteases, indicating that it is a novel metalloprotease belonging to subfamily M12A. Myroilysin had broad specificity and much higher elastinolytic activity than the bacterial elastinase pseudolysin. It is the first reported elastase in M12, to our knowledge. Although it displayed very low activity to collagen, myroilysin had strong collagen-swelling ability and played synergistic role with collagenase in collagen hydrolysis. It can be speculated that myroilysin synergistically interacts with other enzymes in its in situ biotic assemblage and that it may play an important role in the degradation of deep-sea HMW organic nitrogen.
