Oxidation of serotonin and 5-hydroxyindoles during the denaturation of oxyhaemoglobin

Abstract

1959SUMMARY 1. The reactions between chymotrypsin and the p-nitrophenyl ester of N-benzyloxycarbonyl Ltyrosine have been studied by a fast-reaction photometric method.2. It has been shown that an N-benzyloxycarbonyl-L-tyrosine-chymotrypsin compoundis formed as an intermediate in the enzymic hydrolysis of this substrate. The formation of this intermediate compound is so fast (k > 1000 sec.-') that its kinetics could not be studied.3. A comparison of the reaction parameters of the chymotrypsin-catalysed hydrolysis of the amide, ethyl ester and p-nitrophenyl ester of tyrosine gives further support to a three-step reaction scheme for enzymic hydrolysis, which has been previously proposed.We are most grateful to Dr C. J. Martin for a sample of the p-nitrophenyl ester of N-benzyloxycarbonyl-L-tyrosine as well as for some helpful advice.Stacey (1956) reported that serotonin (5-hydroxytryptamine) disappears when it is incubated with washed erythrocytes. In a study of the transport of serotonin into erythrocytes we found no serotonin inside the cells, and it seemed possible that the serotonin was being destroyed by a factor in the erythrocytes. This paper explains why serotonin appeared to be destroyed by erythrocytes. A preliminary report of this work has already appeared (Ling & Blum, 1958).EXPERIMENTAL AND RESULTS Blood (about 15 ml.) was obtained from two rats lightly anaesthetized with ether which were bled from the neck into a polyethylene beaker containing 10 ml. of 0-85% NaCl with either 0-1 g. of ethylenediaminetetra-acetic acid or 6 mg. of heparin. The erythrocytes were then centrifuged for 3 min. at 2000 g and the supernatant fluid was decanted. The cells were resuspended in 47-50 ml. of 0K12M-NaCl-0-04M-Na,HPO4 buffer, pH 7-4. The cells were washed three times in about 40 ml. of this buffer. Blood obtained from other species was treated in the same way. When necessary, the washed erythrocytes were haemolysed by adding 2-5 vol. of water. Crystalline haemoglobin was prepared from dog blood by the procedure of Drabkin (1946).The creatinine sulphate salt of serotonin, bufotenin (NN-dimethylserotonin) mono-oxalate, tryptamine hydrochloride, indol-3-ylacetic acid and 5-hydroxyindol-3-ylacetic acid (5-HIAA) were purchased from the California Biochemical Foundation. Crystalline egg albumin, serum globulin, cytochrome c, glutathione and 5-hydroxytryptophan were purchased from the Nutritional Biochemical Corp. Catalase was purchased from Worthington Biochemicals Inc., haemin from Eastman Organic Chemicals

Synthesis and antitumor and antiviral properties of 5-alkyl-2'-deoxyuridines 3',5'-cyclic monophosphates, and neutral cyclic triesters

“…Curiously, compound 7 was only effective against vaccinia virus. Some of the 5-alkyl-dUrd's, namely 1 (ref 2b), 2 (ref 3), 3 (ref 2b), and 4 (ref 31), have also been the subject of previous antiviral activity studies, and the MIC50 values reported here are in good agreement with those reported earlier. The 5-alkyl-dUMP's 8-14 were not examined for antiviral activity; it is assumed that their antiviral potencies are similar, if not identical, to those of the corresponding dUrd analogues, as has been directly demonstrated for 5-ethyl-dUMP,32 5-propyl-dUMP,32 5fluoro-dUMP,30 5-bromo-dUMP,30 5-iodo-dUMP30, and 5-trifluoromethyl-dUMP.30 Neutral phosphate triesters 22-25 were generally inactive against the viral strains of Table IV at the maximum concentrations tested: 22 (300 µg/mL), 23 (400 µg/mL), 24 (150 µg/mL), and 25 (200 µg/mL).…”

Reply to Lrp5 regulation of bone mass and gut serotonin synthesis

“…4). We included ascorbic acid in our assays of whole-blood serotonin 2 because it prevents hemolysis from destroying serotonin by oxidation 6 , whereas Karsenty and colleagues measured serotonin in frozen heparinized blood without ascorbic acid (Fig. 1e in ref.…”

Serotonin Acts as a Radical Scavenger and Is Oxidized to a Dimer During the Respiratory Burst of Activated Microglia

“…Examples are the enzymatic oxidation of 5-HT by peroxidase (Napolitano et al, 1988;Methodiewa et al, 1989;Svensson, 1989) and the nonenzymatic oxidation of 5-HT by oxyhemoglobin (Blum and Ling, 1959), by ferricytochrome (Alivisatos and Williams-Ashman, 1964), or by inorganic oxidants such as copper and AgNO3 (Eriksen et al, 1960), ammonium persulfate, potassium ferricyanide, and sodium periodate (Napolitano et al, 1988). 5-HT has been also found to be readily oxidized by human serum and erythrocyte hemolysates (Blum and Ling, 1959;Martin et al, 1960), by liver and brain microsomes (Uemura et al, 1980), and by spleen homogenates (Nelson and Huggins, 1975), but the products of these oxidation processes have been only poorly identified. Wrona and Dryhurst (1988) investigated the electrochemical oxidation of 5-HT and proposed an oxidative pathway involving the formation of phenoxyl-and nitrogen-centered radicals that could either couple to give a series of oligomeric products or lose another electron to generate an unstable quinoneimine.…”