乳鐵蛋白( Lactoferrin, LF)是一種非血紅素鐵結(jié)合蛋�,屬于轉(zhuǎn)鐵蛋白家�。乳鐵蛋白大量存在于哺乳動物生物體液中,由黏膜上皮細胞產(chǎn)�,也是人體體液免疫重要的組成部分,連接先天和適�(yīng)性免疫功��
乳鐵蛋白的保護作用有抗癌、抗炎和免疫�(diào)節(jié)活性和抗菌,這些廣泛的保護作用是通過各種生物作用機制實現(xiàn)�,例如乳鐵蛋白結(jié)合鐵的能力,還有乳鐵蛋白與分子和細胞組分的相互作�,使得乳鐵蛋白具有多種獨特的抗微生物活��
隨著生命科學(xué)的不斷發(fā)展,乳鐵蛋白的抗菌機制被廣泛地運用到生物制藥、美容美妝、保健食�、醫(yī)療醫(yī)美等各個產(chǎn)�(yè)。本次小編將匯總多篇文獻證據(jù)為大家盤點乳鐵蛋白抗菌機��
1.乳鐵蛋白的結(jié)�(gòu)
乳鐵蛋白是一個由�700個氨基酸組成�80kDa糖基化蛋白,在物種間具有高度同源�。乳鐵蛋白擁有兩個對稱的同源球狀域:N-�(huán)和C-�(huán);N-�(huán)對應(yīng)于肽鏈中的第1-333個氨基酸殘基,而C-�(huán)與第345-692個氨基酸殘基對應(yīng),這兩個域的兩端由一段短�α-螺旋相連接。每個環(huán)有兩個子�(亞域):N1、N2和C1、C2 組成,并分別包含一個鐵�(jié)合位點和一個糖基化位點 [1]�
乳鐵蛋白三維�(jié)�(gòu)[2]
乳鐵蛋白能結(jié)合多種金屬離子:Fe2+、Fe3+、Cu2+、Zn2+和Mn2+�,它主要以兩種形式存在:富含鐵形式的holo-lactoferrin和不含鐵形式的apo-lactoferrin。兩者有不同的三級結(jié)�(gòu):apo-lactoferrin的特點是有一�“開放�”的N-�(huán)和一�“封閉�”的C-�(huán),而holo-lactoferrin兩個環(huán)都是“封閉�”�[3]�
正是由于乳鐵蛋白可以可逆結(jié)合鐵離子的特性,奠定了其抗菌作用機制的基�(chǔ)�
2.乳鐵蛋白抗細菌機�
大量研究者研究了乳鐵蛋白對于革蘭氏陽性菌(G+)和革蘭氏陰性菌(G-)在體�(nèi)和體外的抑菌性能和機制,簡單匯總?cè)缦拢?/p>
�1 乳鐵蛋白對常見菌株的抑菌機制[2]
乳鐵蛋白�(fā)揮抗菌活性的作用機制可以概括如下�
2.1 鐵隔離或鐵剝奪作用:
鐵離子是大多�(shù)細菌生長所必需的營�(yǎng)物質(zhì),參與了許多重要的生物學(xué)過程。乳鐵蛋白具有較高的鐵離子親和�,可以通過螯合鐵離子與需要鐵離子的細菌競爭性結(jié)合鐵,將鐵離子從細菌病原體中隔離出來,限制細菌在感染部位對這種營養(yǎng)物質(zhì)的使�,抑制細菌的生長,并下調(diào)其毒力因子的表達�
2.2 改變細菌細胞膜的通透性:
乳鐵蛋白能夠與細菌表面分子非特異性結(jié)合,封閉細菌細胞膜上的通道位點,阻斷營�(yǎng)物質(zhì)和細菌蛋白的運�,從而抑制細菌的合成、代�。脂多糖(LPS)為革蘭氏陰性菌細胞外膜的主要成�,乳鐵蛋白通過與脂多糖的相互作用破壞革蘭氏陰性菌的外�,改變細胞膜的通透�[29],達到直接殺菌作�;乳鐵蛋白N-端帶正電荷也可以通過阻止LPS與細菌陽離子(Ca2+和Mg2+)之間的相互作用,有效干擾大腸桿菌的聚集性增�[30]�
2.3 抑制細菌粘附或定植:
乳鐵蛋白的N-末端具有絲氨酸蛋白酶活�,能有效地從流感嗜血桿菌(G-)外膜中提取IgA1蛋白酶前蛋白,還能特異性地降解Hap黏附素并阻斷Hap介導(dǎo)的黏�,從而防止流感嗜血桿菌的定�[31]。乳鐵蛋白具有阻止某些細菌附著在宿主細胞上的能力,粘附抑制的機制尚不清楚,但有研究認�,乳鐵蛋白的寡甘露聚糖結(jié)合細菌粘附素,阻止它們與宿主細胞受體的相互作��
2.4 防止細菌生物膜形成:
生物膜形成是銅綠假單胞菌的一種群聚組織粘附方法,在囊性纖維化患者中得到了充分的研究。通過生物膜的形成,細菌對宿主細胞的防御機制和抗生素的治療�(chǎn)生高度耐藥�,而一些細菌菌株需要高水平的鐵來形成生物膜,推測乳鐵蛋白通過鐵螯合來有效抑制生物膜的形成�
總體而言,乳鐵蛋白是人體�(nèi)具有抗多種微生物活性的重要物質(zhì),是�(gòu)成人體體液免疫的�(guān)鍵組成部�,同時也可以作為生物制劑生產(chǎn)中的生物防腐�,醫(yī)美藥品中抑菌、抗菌成分的重要原料,具有很高的�(jīng)濟價值。目前市面上的乳鐵蛋白主要從牛奶中提�,禾元生物依托自己的專利技�(shù)平臺—— 水稻胚乳細胞生物反應(yīng)器高效重組蛋白質(zhì)表達平臺(OryzHiExp)和重組蛋白純化技�(shù)平臺(OryzPur)開發(fā)了植物源重組人乳鐵蛋白,具有良好的生物活�。植物源重組乳鐵蛋白杜絕了天然乳鐵蛋白中動物�、人源雜�(zhì)的風(fēng)險,也比微生物源重組蛋白擁有更優(yōu)秀的折疊狀�(tài),結(jié)�(gòu)功能與生物活性,為乳鐵蛋白市場提供了更安全更高質(zhì)的選��
參考文�
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[2]Lactoferrin a multiple bioactive protein: an overview.2012
[3]Lactoferrin: a multifunctional protein. 2005
[4]Effect of food components on growth of Basillius stearothermophilus. 1974
[5]Residues in colostrum following antibiotic dry cow therapy. 1984
[6]Inhibition of bacteria by lactoferrin and other iron-chelating agents. 1968
[7]Human milk lactoferrin inactivates two putative colonization factors expressed by Haemophilus inflfluenzae. 1998
[8]Potential antimicrobial effects of human lactoferrin against oral infection with Listeria monocytogenes in mice. 2005
[9]Identification of pneumococcal surface protein A as a lactoferrin-binding protein of Streptococcus pneumoniae. 1999
[10]Both lactoferrin and iron influence aggregation and biofilm formation in Streptococcus mutans . 2004
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[15]Human milk fractions inhibit the adherence of diffusely adherent Escherichia coli (DAEC) and enteroaggregative E. coli (EAEC) to HeLa cells. 2000
[16]Lichtenberger, Recombinant human lactoferrin is effective in the treatment of Helicobacter felis-infected mice. 2000
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[26]Anti-bacterial activity of bovine milk lactoferrin against some mastitis causative pathogens with special regard to mycoplasma. 2010
[27]Periodontitis, periodontopathic bacteria and lacto-ferrin. 2010
[28]Antimicrobial effect of lactoferrin and its amidated and pepsin-digested derivatives against Salmonella enteriditids and Pseudomona fluorescence. 2010
[29]Farnaud S, Evans RW. Lactoferrin--a multifunctional protein with antimicrobial properties. Mol. Immunol.. 2003,
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[31]Human milk lactoferrin inactivates two putative colonization factors expressed by Haemophilus influenzae. 1998