N-Benzoyl-D-lysinol

Inhibition of endothelium-dependent relaxation by NG-monomethyl L-arginine (L-NMMA) and its reversal by excess L- but not D-arginine is used to support the hypothesis that the endothelium-derived relaxing factor (EDRF) is generated exclusively from the metabolism of L-arginine. However, in freshly isolated vascular tissues, L-arginine is a poor vasodilator when compared to the N-substituted arginine compound, N alpha-benzoyl L-arginine ethyl ester (BAEE). Here, we show that such N-substituted compounds are potent hypotensive agents in anesthetized rats. In contrast, L-arginine elicits hypotensive effect only at higher concentrations (greater than 100 mg/kg). This effect of L-arginine is not antagonized by L-NMMA. Furthermore, D-arginine, L-homoarginine and L-lysine also have hypotensive effects at these concentrations. Indomethacin treatment partially attenuates the hypotensive effects of the basic amino acids. In contrast, the hypotensive effect of BAEE is antagonized by L-NMMA in a dose-dependent manner and by methylene blue, which is an inhibitor of soluble guanylate cyclase. In addition, substitution at the arginine moiety determines the hypotensive effect. When the amino acid glycine is inserted between the benzoyl group and arginine as in benzoyl-glycine-arginine, significant attenuation of the hypotensive effect is observed. These data demonstrate that compounds such as BAEE generate an EDRF-like agent in vivo and basic amino acids such as L-arginine elicit hypotension at concentrations above 100 mg/kg by mechanisms other than the generation of EDRF.

We report a plug-and-play strategy for the preparation of functionally enhanced antibodies with a defined average degree of conjugation (DoC). The first stage (plug) allows the controllable and efficient installation of azide groups on lysine residues of a native antibody using 4-azidobenzoyl fluoride. The second step (play) allows for versatile antibody functionalization with a single payload or combination of payloads, such as a toxin, a fluorophore, or an oligonucleotide, via copper-free strain-promoted azide-alkyne cycloaddition (SPAAC). It is notable that in comparison to a classical N-hydroxysuccinimide ester (NHS) strategy, benzoyl fluorides show faster and more efficient acylation of lysine residues in a PBS buffer. This translates into better control of the DoC and enables the efficient and fast functionalization of delicate biomolecules at low temperature.

The objective of this study was to ascertain whether endothelium-dependent relaxation and guanosine 3',5'-cyclic monophosphate (cGMP) formation in bovine pulmonary artery are dependent on L-arginine. Arterial rings responded to acetylcholine and A23187 with increased cGMP accumulation and relaxation and showed resting L-arginine levels of approximately 300 microM. Addition of L-arginine failed to cause relaxation or cGMP accumulation. Arterial rings incubated under tension at 37 degree C for 24 h showed a three- to fourfold decline in L-arginine levels, and this decline was accompanied by a similar decline in resting cGMP levels as well as complete refractoriness to endothelium-dependent relaxation and cGMP formation in response to acetylcholine and A23187, without alteration of responsiveness to nitric oxide, s-nitrosothiols, or nitroglycerin. The endothelium in 24-h incubated arterial rings was normal morphologically, as assessed by scanning electron microscopy. L-Arginine caused endothelial-dependent relaxation and cGMP formation in L-arginine-depleted rings, which was antagonized by oxyhemoglobin and methylene blue. Bovine aortic endothelial cells grown in L-arginine-deficient medium supplemented with D-arginine during the final 24 h of growth failed to generate endothelium-derived nitric oxide, as assessed by bioassay cascade. L-Canavanine, but not L-lysine or L-ornithine, protected against the decline in L-arginine and cGMP levels and loss of endothelium-dependent relaxation that was characteristic of 24-h incubated arterial rings. The pharmacological properties of L-arginine were shared by L-arginine ethyl ester, L-arginine methyl ester, and L-homoarginine but not N-alpha-benzoyl-L-arginine ethyl ester or L-canavanine. These observations indicate that L-arginine or a structural analogue may be obligatory for endothelium-dependent relaxation and cGMP formation.