Catalysis uncoupling in a glutamine amidotransferase bienzyme by unblocking the glutaminase active site.

Nitrogen is incorporated into various metabolites by multifunctional glutamine amidotransferases via reactive ammonia generated by glutaminase hydrolysis of glutamine. Although this process is generally tightly regulated by subsequent synthase activity, little is known about how the glutaminase is inhibited in the absence of an activating signal. Here, we use imidazoleglycerolphosphate synthase as a model to investigate the mechanism of glutaminase regulation.

Bond dissociation of the dipeptide dialanine and its derivative alanine anhydride induced by low energy electrons.

Dissociative electron attachment to dialanine and alanine anhydride has been studied in the gas phase utilizing a double focusing two sector field mass spectrometer. We show that low-energy electrons (i.e.

Ion-molecule reactions of ammonia clusters with C60 aggregates embedded in helium droplets.

Helium nanodroplets are co-doped with C(60) and ammonia. Mass spectra obtained by electron ionization reveal cations containing ammonia clusters complexed with up to four C(60) units. The high mass resolution of Δm/m≈ 1/6000 makes it possible to separate the contributions of protonated, unprotonated and dehydrogenated ammonia.