Amino acid-containing acyloxyacyl lipids are composed of a 3-hydroxy fatty acid amide-bound to the α-amino group of an amino acid. A second fatty acid is ester-linked to the 3-hydroxy group of the first fatty acid. Most commonly, ornithine is the headgroup of these lipids, but glycine, serineglycine, glutamine and lysine have also been described in bacteria. Ornithine lipids (OL) can be synthesized by about 50% of the sequenced bacterial species, and several covalent modifications of its basic structure have been described. The OL hydroxylase OlsE is widespread in Rhizobium and Agrobacterium species and is responsible for introducing a hydroxyl group at a hence unknown position within the ornithine headgroup causing the formation of the OL named S2. Using NMR on purified OL S2, we show that the OlsE-mediated hydroxylation takes place at the C-4 position of the ornithine headgroup. Furthermore, we identify a hydroxylase in the genome of Pseudopedobacter saltans, distantly related to OlsE from α-proteobacteria, able to hydroxylate the headgroup of both ornithine lipids and lysine lipids. A homology search with the amino acid sequence of this hydroxylase allows us to predict that OL headgroup hydroxylation is not restricted to a few α-proteobacteria, but is apparently also common in many genera belonging to the Cytophaga-Flavobacterium-Bacteroidetes (CFB) group of bacteria.

含氨基酸的酰氧基酰基脂质由结合到氨基酸的α-氨基上的3-羟基脂肪酸酰胺组成。第二脂肪酸酯键合至第一脂肪酸的3-羟基。最常见的是鸟氨酸是这些脂质的头基，但是细菌中也描述了甘氨酸，丝氨酸甘氨酸，谷氨酰胺和赖氨酸。鸟氨酸脂质（OL）可以由大约50％的测序细菌物种合成，并且已经描述了其基本结构的几种共价修饰。OL羟化酶OlsE广泛存在于根瘤菌和土壤杆菌中物种并负责在鸟氨酸头基团内一个未知位置引入羟基，从而导致形成名为S2的OL。在纯化的OL S2上使用NMR，我们显示OlsE介导的羟基化发生在鸟氨酸头基的C-4位置。此外，我们确定了假单歧杆菌盐基因组中的羟化酶，与α-变形杆菌中的OlsE远缘相关，能够羟化鸟氨酸脂和赖氨酸脂的头基。通过与该羟化酶氨基酸序列的同源性搜索，我们可以预测OL头基羟基化不仅限于少数α-变形杆菌，而且显然在许多属于Cytophaga-Flavobacterium-Bacteroidetes（CFB）属的属中也很常见。细菌。