对于我们来说,这是一种替代治疗。”来自希腊的研究带头人Ilias Karaiskos博士说,“我们认为如果我们有喹诺酮可以使用,那我们就应该使用喹诺酮,因为许多研究表明喹诺酮在前列腺药效充足,进入前列腺组织内的能力最强。但如果患者体内的病原微生物对喹诺酮产生耐药性,那我会用磷霉素。”
化学性质磷霉素是一种熔点约94℃的结晶体。临床一般使用其钠盐或钙盐,其中钠盐常用于注射,而钙盐则适用于口服。其钠盐为白色结晶性粉末,具有强烈的吸湿性,极易溶于水,微溶于乙醇和某些有机溶剂;而其钙盐为白色粉末,微溶于水,不溶于丙酮、苯、氯仿及乙醚。
用途磷霉素是一种广谱抗生素,通过阻止细菌细胞壁的合成而具有杀菌作用,对革兰氏阳性及阴性菌都有效。主要用于治疗由金黄色葡萄球菌、大肠杆菌、奇异变形杆菌、痢疾杆菌等引起的感染。
此外,它还对绿脓杆菌、变形杆菌、大肠杆菌、沙雷氏菌和某些类型的葡萄球菌有很好的疗效。
生产方法磷霉素的生产以丙炔醇为原料,经酯化、重排、水解、异构化等一系列步骤得到丙炔基磷酸二钠。随后通过进一步的水解、异构化及氢化反应生成顺丙烯磷酸。最后与(±)-a-苯乙胺成盐,并经过环氧化和拆分而最终制得磷霉素。
Phosphonate natural products possess a range of biological activities as a consequence of their ability to mimic phosphate esters or tetrahedral intermediates formed in enzymatic reactions involved in carboxyl group metabolism. The dianionic form of these compounds at pH 7 poses a drawback with respect to their ability to mimic carboxylates and tetrahedral intermediates. Microorganisms producing phosphonates have evolved two solutions to overcome this hurdle: biosynthesis of monoanionic phosphinates containing two P-C bonds or esterification of the phosphonate group. The latter solution was first discovered for the antibiotic dehydrophos that contains a methyl ester of a phosphonodehydroalanine group. We report here the expression, purification, substrate scope, and structure of the
FosB is a divalent-metal-dependent thiol-S-transferase implicated in fosfomycin resistance among many pathogenic Gram-positive bacteria. In the present paper, we describe detailed kinetic studies of FosB from Staphylococcus aureus (SaFosB) that confirm that bacillithiol (BSH) is its preferred physiological thiol substrate. SaFosB is the first to be characterized among a new class of enzyme (bacillithiol-S-transferases), which, unlike glutathione transferases, are distributed among many low-G+C Gram-positive bacteria that use BSH instead of glutathione as their major low-molecular-mass thiol. The Km values for BSH and fosfomycin are 4.2 and 17.8 mM respectively. Substrate specificity assays revealed that the thiol and amino groups of BSH are essential for activity, whereas malate is important for SaFosB recognition and catalytic efficiency. Metal activity assays indicated that Mn2+ and Mg2+ are likely to be the relevant cofactors under physiological conditions. The serine analogue of BSH (BOH) is an effective competitive inhibitor of SaFosB with respect to BSH, but uncompetitive with respect to fosfomycin. Coupled with NMR characterization of the reaction product (BS–fosfomycin), this demonstrates that the SaFosB-catalysed reaction pathway involves a compulsory ordered binding mechanism with fosfomycin binding first followed by BSH which then attacks the more sterically hindered C-1 carbon of the fosfomycin epoxide. Disruption of BSH biosynthesis in S. aureus increases sensitivity to fosfomycin. Together, these results indicate that SaFosB is a divalent-metal-dependent bacillithiol-S-transferase that confers fosfomycin resistance on S. aureus.
Fosfomycin is a wide-spectrum antibiotic that is used clinically to treat acute cystitis in the United States. The compound is produced by several strains of streptomycetes and pseudomonads. We sequenced the biosynthetic gene cluster responsible for fosfomycin production in