Chemical modification of peptides by hydrazine.

High pressure ('performance') liquid chromatography on reverse-phase supports has been used to characterize the products arising from the hydrazine treatment of peptides. In addition to converting arginine residues into ornithine, the reaction was found to cleave predominately Gly-Xaa, Xaa-Gly, Asn-Xaa and Xaa-Ser peptide bonds. Peptide-bond cleavage and deguanidation was studied as a function of time of exposure to hydrazine, hydrazine concentration and temperature. The convenience of this method of chromatography for the rapid low-cost separation and isolation of peptides, as well as their reaction products, is illustrated at the level of material required for solid-phase microsequencing.     

The effects of hydrazine on sickle cells

The response of the red cells from patients with sickle cell disease to hydrazine treatment in vitro is to inhibit the sickled morphology, while the metabolic characteristics and the osmotic fragility of the cells remain unaltered. However, the oxygen affinity of the sickle cell haemoglobin is decreased.     

Effect of hydrazine, isonicotinic acid hydrazide, hydrazine sulfate, and dimethylhydrazine on guanylate cyclase activity.

The chemical carcinogen hydrazine is a potent stimulator of guanylate cyclase. In the present investigation we found that three chemical carcinogens structurally related to hydrazine, isonicotinic acid hydrazide, hydrazine sulfate, and dimethylhydrazine, decreased guanylate cyclase activity. It is of interest that hydrazine has been shown to increase DNA synthesis whereas isonicotinic acid hydrazide, hydrazine sulfate, and dimethylhydrazine decrease DNA synthesis. The relationship, if any, linking the guanylate cyclase-cyclic GMP system to DNA synthesis and carcinogenesis remains to be explored.     

Effect of hydrazine on properties of cytochrome oxidase

The effects of hydrazine on ferrocytochrome c oxidation by cytochrome oxidase and on spectral properties of the enzyme were studied. Hydrazine was found to modify the spectral properties of lipid-depleted preparations of cytochrome oxidase dissolved in 1% cholate and to inhibit the cytochrome c oxidase activity of the enzyme, whereas the kinetic properties of lipid-enriched and Tween preparations were unchanged by hydrazine. Cytochrome oxidase was found to possess a hydrazine oxidase activity. This activity was not coupled with the specific cytochrome c oxidase activity. The effect of pH on the observed changes was studied. Hydrazine was found to yield protein bands in the optical spectra of cytochrome oxidase as 580 nm, 537 nm and 845 nm. It is concluded that hydrazine interacts with the oxygen-binding site of cytochrome oxidase. The effect of hydrazine on the formation of the "ferryl" form (Fe4+a3/Cu2+b) of the enzyme is discussed.     

Lipase catalysed acylation of hydroxylamine and hydrazine derivatives

The lipase catalysed acylation of hydroxylamine-and hydrazine as well as their derivatives by octanoic acid is very efficient. Cross-linked crystals of Candida rugosa lipase (ChiroCLEC-CR) mediated the conversion of racemic ibuprofen into (S)-ibuproxam. A number of lipases also catalysed the condensation of hydrazine with an excess of octanoic acid giving N,N′-dioctanoylhydrazine. The hydrazide of 2-(4-isobutylphenyl)propanoic acid (ibuprofen), prepared by non-enzymatic reaction of ibuprofen methyl ester with hydrazine, acted as nucleophile towards several lipases that do not accept ibuprofen derivatives as acyl donor.     

Carbonyl scavenger and antiatherogenic effects of hydrazine derivatives

Reactive carbonyl compounds (RCC) generated by polyunsaturated fatty acid oxidation alter progressively cellular and tissular proteins by forming adducts on free amino groups and thiol residues (carbonyl stress). Carbonyl scavengers may neutralize RCC, but their protective effect in atherosclerosis has not been extensively studied. We report the carbonyl scavenger and antiatherogenic properties of hydrazine derivatives, namely hydralazine, an antihypertensive drug, isoniazid, an antituberculosis agent, and two antidepressants, phenelzine and iproniazid. These drugs were poorly efficient in preventing the oxidation of LDL mediated by smooth muscle cells (SMCs), but inhibited the toxicity of UV-oxidized LDL (oxLDL) and of 4-hydroxynonenal (4-HNE). Hydrazine derivatives prevented the formation of foam cells resulting from LDL oxidation in human macrophagic U937 cells, and blocked the carbonyl stress in SMCs, by inhibiting the decrease in free amino group content, the increase in carbonylated proteins, and the formation of 4-HNE adducts on PDGFR. Experimental studies carried out on apoE-/- mice supplemented with drugs (30 mg/L in drinking water) showed a significant carbonyl stress inhibition correlated with a net reduction of atherosclerotic lesion development. In conclusion, these data indicate that hydrazine derivatives exhibit carbonyl scavenger and antiatherogenic properties, which opens novel therapeutical approaches for atherosclerosis and its cardiovascular complications.     

Enzymatic activation of hydrazine derivatives. A spin-trapping study

The oxidative metabolism of hydralazine, isoniazid, iproniazid, and phenylhydrazine has been studied using spin-trapping techniques. The oxidation of these hydrazine derivatives, catalyzed by horseradish peroxidase and prostaglandin synthetase, produces reactive free radical intermediates. Enzymatic activation of hydralazine produce the nitrogen-centered hydralazyl radical (RNHNH); phenylhydrazine formed only the phenyl radical. Iproniazid, on the other hand, formed both the isopropyl radical and a hydroperoxy radical. The formation of the hydroperoxy radical was not inhibited by superoxide dismutase. The horseradish peroxidase-catalyzed oxidation of isoniazid produced two different carbon-centered radicals. The identity of these radicals is not clear; however, they may arise from an acyl (RCO) radical and an alkyl (R) radical.