Genetic diseases of the Kennedy pathways for membrane synthesis.

The two branches of the Kennedy pathways (CDP-choline and CDP-ethanolamine) are the predominant pathways responsible for the synthesis of the most abundant phospholipids, phosphatidylcholine and phosphatidylethanolamine, respectively, in mammalian membranes. Recently, hereditary diseases associated with single gene mutations in the Kennedy pathways have been identified. Interestingly, genetic diseases within the same pathway vary greatly, ranging from muscular dystrophy to spastic paraplegia to a childhood blinding disorder to bone deformations. Indeed, different point mutations in the same gene (PCYT1; CCTα) result in at least three distinct diseases. In this review, we will summarize and review the genetic diseases associated with mutations in genes of the Kennedy pathway for phospholipid synthesis. These single-gene disorders provide insight, indeed direct genotype-phenotype relationships, into the biological functions of specific enzymes of the Kennedy pathway. We discuss potential mechanisms of how mutations within the same pathway can cause disparate disease.

m-s-m Cationic Gemini and Zwitterionic Surfactants-Spacer-Dependent Synergistic Interactions.

Critical micelle concentration (cmc) values were determined for the mixed zwitterionic/cationic gemini systems of N-dodecyl- N, N-dimethyl-3-ammonio-1-propanesulfonate (ZW3-12)/ N, N'-bis(dimethyldodecyl)-α,ω-alkanediammonium dibromide (12-s-12) systems. The cmc values for the mixed systems were determined through conductivity measurements. The degree of nonideality of the interaction in the mixed micelle (ßm), for each system, was determined according to Rubingh's nonideal solution theory. In most cases, the systems exhibited negative deviations (-ßm values) at high surfactant mole fractions of zwittergent (αZW3-12). Specifically, the ZW3-12/12-4-12 system displayed -ßm values at αZW3-12 ≥ 0.5, while both the ZW3-12/12-5-12 and the ZW3-12/12-6-12 systems displayed -ßm values over the entire mole fraction range. Except for the low mole fraction range in the 12-4-12 system, these mixed surfactant systems demonstrated almost identical behavior to the n-dodecyltrimethylammonium bromide/12-2-12 system studied by Bakshi et al. providing further evidence that ZW3-12 tends to behave as a cationic surfactant in mixed surfactant systems. The manner in which the cosurfactants aggregate in the micelles was determined via two-dimensional (2D) NOESY spectroscopy. In the case of both the ZW3-12/12-5-12 and the ZW3-12/12-6-12 systems, the 2D NOESY spectra exhibited strong cross peaks between the gemini and zwitterionic surfactants over the entire micellar composition range. In the case of the ZW3-12/12-4-12 system, little cross peak intensity was observed between the gemini and the zwitterionic surfactant at low micellar compositions of the zwittergent. The results suggest some micelle demixing is occurring between the gemini and the zwittergent certain micellar composition ranges, a phenomenon rarely associated with hydrocarbon surfactants.

Antimicrobial activities of jadomycin B and structurally related analogues.

Natural products are leads for new antibiotics as a result of their structural complexity and diversity. We have isolated a series of structurally related polyketide-derived natural products from Streptomyces venezuelae ISP5230. The most active of these jadomycin analogues showed good activity against a variety of staphylococci, including methicillin-resistant Staphylococcus aureus.

Stereochemical integrity of oxazolone ring-containing jadomycins.

The jadomycins are a series of natural products produced by Streptomyces venzuelae ISP5230 in response to ethanol shock. A unique structural feature of these angucyclines is the oxazolone ring, the formation of which is catalyzed by condensation of a biosynthetic aldehyde intermediate and an amino acid. The feeding of enantiomeric forms of alpha-amino acids indicates that the amino acid is incorporated by S. venezuelae ISP5230 without isomerization at the alpha-carbon. The characterization of the first two six-membered E-ring-containing jadomycins is reported. These precursor-directed biosynthesis studies indicate flexibility in the acceptor substrate specificity of the glycosyltransferase, JadS. Analysis of cytotoxicity data against two human breast cancer cell lines indicates that the nature of the substitution at the alpha-carbon, rather than the stereochemistry, influences biological activity.

Substrate flexibility of a 2,6-dideoxyglycosyltransferase.

We report the first 2,6-dideoxysugar-O-glycosyltransferase with substrate flexibility at the 2 position, confirm the function of a putative NDP-hexose 2,3-dehydratase in the jadomycin B biosynthetic gene cluster and deduce the substrate flexibility of downstream enzymes in l-digitoxose assembly, enabling reprogramming of biosynthetic gene clusters to modify sugar substituents.

Novel and expanded jadomycins incorporating non-proteogenic amino acids.

Jadomycin B is a secondary metabolite produced, in response to stress, by Streptomyces venezuelae ISP5230 grown in nutrient-deprived media. We present definitive electrospray ionization mass spectrometry data identifying a series of novel jadomycins with non-proteogenic amino acids incorporated into the oxazolone ring of the secondary metabolite, and strengthening evidence for the existence of an aldimine intermediate in the biosynthetic pathway. We also demonstrate that the size of the oxazolone ring can be expanded by incorporating beta-amino acids.