Specific Detection of Cellular Glutamine Hydrolysis in Live Cells Using HNCO Triple Resonance NMR

Glutamine plays key roles as a biosynthetic precursor or an energy source in cancers, and interest in its metabolism is rapidly growing. However, the proper evaluation of glutamine hydrolysis, the very first reaction in the entire glutaminolysis, has been difficult. Here, we report a triple resonance NMR-based assay for specific detection of glutaminase activity carrying out this reaction using stable-isotope labeled glutamine. Compared to conventional methods involving coupled enzyme assays, the proposed approach is direct because it detects the presence of the H–N–CO amide spin system. In addition, the method is unique in enabling the measurement of glutamine hydrolysis reaction in real-time in live cells. The approach was applied to investigating the effects of a glutaminase inhibitor and the inhibitory effects of glucose on glutamine metabolism in live cells. It can be easily applied to studying other signals that affect cellular glutamine metabolism

Structure Assignment of Lucentamycin E and Revision of the Olefin Geometries of the Marine-Derived Lucentamycins

A new lucentamycin analogue, lucentamycin E (<b>5</b>), was isolated from the culture broth of the marine-derived actinomycete <i>Nocardiopsis lucentensis</i>, strain CNR-712. The absolute stereostructure of <b>5</b> was assigned by comprehensive analyses of NMR data and by application of the advanced Marfey’s method. The planar structure of <b>5</b> was analogous to lucentamycins A–D, whereas the olefin geometry of the 3-methyl-4-ethylideneproline moiety was found to be <i>E</i>, opposite of that previously reported. Consequently, a reinvestigation of the olefin geometries of the 3-methyl-4-ethylideneproline residues of lucentamycins A–D showed that the olefin geometries of the substituted proline functionalities must be revised to (2<i>S</i>,3<i>R</i>,<i>E</i>)-3-methyl-4-ethylideneproline

Salinazinones A and B: Pyrrolidinyl-Oxazinones from Solar Saltern-Derived <i>Streptomyces</i> sp. KMF-004

Salinazinones A (<b>1</b>) and B (<b>2</b>), two unprecedented pyrrolidinyl-oxazinones, were isolated from the culture broth of <i>Streptomyces</i> sp. KMF-004 from a solar saltern at Aphae Island, Korea. The structures of these salinazinones, which are unusual and consist of 2-methylpropenyl-1,3-oxazin-6-one bearing 1-oxopyrrolidinyl substituents, were assigned by spectral and chemical analyses using Mosher’s method, circular dichroism (CD), and calculated ECD. Salinazinones are the first examples of a natural alkaloid class composed of an oxazinone–pyrrolidone conjugate