Structure and Function of ArnD. A Deformylase Essential for Lipid A Modification with 4-Amino-4-deoxy-l-arabinose and Polymyxin Resistance.

Covalent modification of lipid A with 4-deoxy-4-amino-l-arabinose (Ara4N) mediates resistance to cationic antimicrobial peptides and polymyxin antibiotics in Gram-negative bacteria. The proteins required for Ara4N biosynthesis are encoded in the and loci, with ArnT ultimately transferring the amino sugar from undecaprenyl-phospho-4-deoxy-4-amino-l-arabinose (C55P-Ara4N) to lipid A. However, Ara4N is N-formylated prior to its transfer to undecaprenyl-phosphate by ArnC, requiring a deformylase activity downstream in the pathway to generate the final C55P-Ara4N donor.

Determination of Substrate Preferences for Desaturases and Elongases for Production of Docosahexaenoic Acid from Oleic Acid in Engineered Canola.

Production of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in plant seed oils has been pursued to improve availability of these omega-3 fatty acids that provide important human health benefits. Canola (Brassica napus), through the introduction of 10 enzymes, can convert oleic acid (OLA) into EPA and ultimately DHA through a pathway consisting of two elongation and five desaturation steps. Herein we present an assessment of the substrate specificity of the seven desaturases and three elongases that were introduced into canola by expressing individual proteins in yeast.

Distinct Roles for Intracellular and Extracellular Lipids in Hepatitis C Virus Infection.

Hepatitis C is a chronic liver disease that contributes to progressive metabolic dysfunction. Infection of hepatocytes by hepatitis C virus (HCV) results in reprogramming of hepatic and serum lipids. However, the specific contribution of these distinct pools of lipids to HCV infection remains ill defined.

Atypical antipsychotics rapidly and inappropriately switch peripheral fuel utilization to lipids, impairing metabolic flexibility in rodents.

Patients taking atypical antipsychotics are frequented by serious metabolic (eg, hyperglycemia, obesity, and diabetes) and cardiac effects. Surprisingly, chronic treatment also appears to lower free fatty acids (FFAs). This finding is paradoxical because insulin resistance is typically associated with elevated not lower FFAs.

Extraction and identification by mass spectrometry of undecaprenyl diphosphate-MurNAc-pentapeptide-GlcNAc from Escherichia coli.

Undecaprenyl diphosphate-MurNAc-pentapeptide-GlcNAc (lipid II) is extracted from Escherichia coli cells by utilizing its unusual pH-dependent solubility property in a Bligh-Dyer system, and identified by electrospray ionization mass spectrometry in conjunction with a novel 15N mass shift analysis. The described approach will facilitate the structural characterization of lipid II variants from diverse bacteria, including antibiotic-resistant mutants, as well as the numerous minor uncharacterized lipids present in all biological systems.

Structure and function of both domains of ArnA, a dual function decarboxylase and a formyltransferase, involved in 4-amino-4-deoxy-L-arabinose biosynthesis.

Modification of the lipid A moiety of lipopolysaccharide by the addition of the sugar 4-amino-4-deoxy-L-arabinose (L-Ara4N) is a strategy adopted by pathogenic Gram-negative bacteria to evade cationic antimicrobial peptides produced by the innate immune system. L-Ara4N biosynthesis is therefore a potential anti-infective target, because inhibiting its synthesis would render certain pathogens more sensitive to the immune system. The bifunctional enzyme ArnA, which is required for L-Ara4N biosynthesis, catalyzes the NAD(+)-dependent oxidative decarboxylation of UDP-glucuronic acid to generate a UDP-4'-keto-pentose sugar and also catalyzes transfer of a formyl group from N-10-formyltetrahydrofolate to the 4'-amine of UDP-L-Ara4N.

A formyltransferase required for polymyxin resistance in Escherichia coli and the modification of lipid A with 4-Amino-4-deoxy-L-arabinose. Identification and function oF UDP-4-deoxy-4-formamido-L-arabinose.

Modification of the phosphate groups of lipid A with 4-amino-4-deoxy-L-arabinose (L-Ara4N) is required for resistance to polymyxin and cationic antimicrobial peptides in Escherichia coli and Salmonella typhimurium. We previously demonstrated that the enzyme ArnA catalyzes the NAD+-dependent oxidative decarboxylation of UDP-glucuronic acid to yield the UDP-4''-ketopentose, uridine 5'-diphospho-beta-(L-threo-pentapyranosyl-4''-ulose), which is converted by ArnB to UDP-beta-(L-Ara4N). E.

The biosynthetic gene cluster for a monocyclic beta-lactam antibiotic, nocardicin A.

The monocyclic beta-lactam antibiotic nocardicin A is related structurally and biologically to the bicyclic beta-lactams comprised of penicillins/cephalosporins, clavams, and carbapenems. Biosynthetic gene clusters are known for each of the latter, but not for monocyclic beta-lactams. A previously cloned gene encoding an enzyme specific to the biosynthetic pathway was used to isolate the nocardicin A cluster from Nocardia uniformis.

Origin of lipid A species modified with 4-amino-4-deoxy-L-arabinose in polymyxin-resistant mutants of Escherichia coli. An aminotransferase (ArnB) that generates UDP-4-deoxyl-L-arabinose.

In Escherichia coli and Salmonella typhimurium, addition of the 4-amino-4-deoxy-l-arabinose (l-Ara4N) moiety to the phosphate group(s) of lipid A is required for resistance to polymyxin and cationic antimicrobial peptides. We have proposed previously (Breazeale, S. D.

Oxidative decarboxylation of UDP-glucuronic acid in extracts of polymyxin-resistant Escherichia coli. Origin of lipid a species modified with 4-amino-4-deoxy-L-arabinose.

Addition of the 4-amino-4-deoxy-l-arabinose (l-Ara4N) moiety to the phosphate groups of lipid A is implicated in bacterial resistance to polymyxin and cationic antimicrobial peptides of the innate immune system. The sequences of the products of the Salmonella typhimurium pmrE and pmrF loci, both of which are required for polymyxin resistance, recently led us to propose a pathway for l-Ara4N biosynthesis from UDP-glucuronic acid (Zhou, Z., Lin, S.