RESUMO
To modify the flavor properties of tomato fruits, cucumber fatty acid hydroperoxide lyase (HPL), which can act on 9-hydroperoxides of fatty acids to form volatile C9-aldehydes, was introduced to tomato plants. Through enzyme assay, high activity of the introduced HPL could be found in either the leaves or fruits of transgenic tomatoes; however, the composition of volatile short-chain aldehydes and alcohols in the transgenic tomato fruits was little modified. This was unexpected because tomato fruits have high lipoxygenase activity to form 9-hydroperoxides. When linoleic acid was added to a crude homogenate prepared from the transgenic tomato fruits, a high amount of C9-aldehyde was formed, but the amount of C6-aldehyde was almost equivalent to that in nontransgenic tomatoes. Through quantification of fatty acid hydroperoxides, it has been revealed that 13-hydroperoxides of fatty acids are preferably formed from endogenous substrate, whereas 9-hydroperoxides are formed from fatty acids added exogenously. From these observations, possible mechanisms to regulate metabolic flow of the lyase pathway are discussed.
Assuntos
Hidroliases/genética , Solanum lycopersicum/genética , Aldeídos/metabolismo , Hidroliases/metabolismo , Solanum lycopersicum/enzimologia , TransgenesRESUMO
Phosphorus nuclear magnetic resonance spectra of whole, mandibular and parotid salivas from healthy humans all presented single broad inhomogeneous lines, the widths arising from the chemical-shift distribution of the resonances of the constituent inorganic phosphate compounds. Spin lattice relaxation of phosphorus in the stimulated parotid saliva was characterized by a single time constant of T1, whereas the spin spin relaxation was found to be determined by the chemical exchange rates. The results indicate that calcium phosphates found in parotid saliva are involved in at least two chemical exchange processes. The dissociation rates for the fast and slow exchange were estimated to be 1.5/sec and 0.2/sec, respectively.
Assuntos
Saliva/metabolismo , Adulto , Fenômenos Químicos , Físico-Química , Feminino , Humanos , Espectroscopia de Ressonância Magnética/instrumentação , Espectroscopia de Ressonância Magnética/métodos , Masculino , Isótopos de Fósforo , Valores de Referência , Saliva/química , TemperaturaRESUMO
Of gustatory-stimulated human whole, parotid, submandibular and sublingual saliva only parotid saliva, a serous rather than mucous secretion, presented a relatively well-resolved proton NMR spectrum with satisfactory signal-to-noise ratio in a short time (30 min). The proton signal intensities showed significant circadian rhythms related to the circadian rhythms of protein concentrations in saliva. Age- and sex-associated differences in spectra were not observed for healthy saliva. On the other hand, marked differences in the spectra were observed for patients with suspected sialoadenitis.
