Enzymatic and immunological evidence for two forms of carnosinase in the mouse.

Carnosinase (aminoacyl-L-histidine hydrolase, EC 3.4.13.3) hydrolyzes the dipeptide carnosine (beta-alanyl-L-histidine), which is thought to play a role in cerebral and skeletal muscular function and has been implicated as a neuroaffector in the olfactory bulb. Carnosinase activity is present in many tissues of the mouse including heart, liver and lung, but it is most active in kidney, uterus and nasal olfactory mucosa. Kinetic measurements with 1H-NMR spectroscopy indicate that the enzyme is stereospecific and can hydrolyze L-but not D-carnosine. Anserine is a poorer substrate, while homocarnosine is essentially a non-substrate. However, these two dipeptides are effective inhibitors of the hydrolysis of L-carnosine. Carnosinase activity is unaffected when assayed in 2H2O at 99% isotopic purity. From considerations of the effect of Mn2+ on (1) substrate concentration velocity curves; (2) thermostability, and (3) inhibitor behavior, tissues with carnosinase can be divided into two groups. Kidney, uterus and olfactory mucosa represent one group, while central nervous system, muscle, spleen, etc. represent the second. The validity of this classification is confirmed by immunological evidence. Antiserum prepared against carnosinase purified from kidney cross-reacts with and inhibits the activity of olfactory mucosa, kidney and uterus but not that from central nervous system, heart or liver.

The complete assignment of the 13C NMR spectra of lasalocid and the sodium salt-complex of the antibiotic.

All thirty-four signals observed in the 13C nmr of both the free acid form (Ia) and sodium salt (Ib) of the polyether antibiotic lasalocid have been assigned. This was achieved using model compounds such as 3-methylsalicylic acid, the retroaldol ketones from both lasalocid and lysocellin and a gamma-lactone from a third polyether, salinomycin. The last assignments to be made were accomplished using biosynthetically enriched samples of the antibiotic.

Carnosine in olfaction : Proton magnetic resonance spectral evidence for tissue-specific carnosine binding sites.

The amount and specificity of binding ofL-carnosine (ß-alanyl-L-histidine) by crude soluble and particulate fractions of several tissues were investigated with proton magnetic resonance ((1)HMR) spectrometry. It was found that the particulate fraction of only nasal olfactory mucosa exhibited a specific binding requiring a particular orientation of the carnosine molecule relative to the binding site. This suggests that whatever role carnosine may play in olfaction is expressed within the nasal olfactory mucosa rather than elsewhere in the olfactory pathway. Possible binding of carnosine to carnosinase was observed in the soluble fractions of nasal olfactory mucosa and kidney. However, the bulk of the carnosine present in the nasal olfactory mucosa in vivo probably is not bound within the cells of this tissue as a complex with soluble protein. These observations are of interest because the nasal olfactory mucosa is the neural tissue that has the highest activities of the enzymes catalyzing the synthesis and degradation of carnosine.The results of this investigation indicate that(1)HMR spectrometry will prove useful for the measurement of transmitter/receptor recognition. The significance of these results in the general context of measurement of "specific" binding interactions by biological samples is discussed, and a basic description of the application of(1)HMR spectrometry to these measurements is presented.

Synthesis of tetrazole ribonucleosides and their evaluation as antiviral agents.

Synthesis of 1-beta-D-ribofuranosyltetrazole and two 5-substituted derivatives, i.e., the 5-carboxamide and 5-acetamide, is described. The stereochemical structure of the parent tetrazole ribonucleoside has been established by means of nuclear Overhauser effect and x-ray crystallography. By analogy to the parent compound, the two 5-substituted tetrazole nucleosides are also assigned the beta configuration on the basis of the NMR coupling constant of the anomeric proton and the site of N-ribosylation is determined by 13C NMR studies. Results are also presented on antiviral testing of these synthetic tetrazole nucleosides against influenza A2/Asian/J-305 virus infection in mice.