PubMed Health⌕ Search

Biomedical subjects

J R KAHN

Publications and source records attributed to J R KAHN.

At least 19 recordsLinked to original sources
PubMed1964

THE PRESENCE OF RENIN ACTIVITY IN BLOOD VESSEL WALLS.

The preparation, of an extract of hog blood vessels and organs containing renin activity has been described. The extract hydrolyzes natural or synthetic renin substrate to form a vasopressor material. This reaction could not be distinguished from the hydrolysis of renin substrates by kidney renin. The activation energy, effect of substrate concentration on velocity, inhibition by antirenin, and pH optimum of the extract and of kidney renin are the same. Renin activity is found in the adventitia and media of the aorta, the liver and, to a lesser extent, in other vascular organs.

Angiotensins↗
PubMed1963

The purification and partial characterization of several forms of hog renin substrate.

Hog renin substrate has been separated into three major (A, B, and C) and two minor forms (D and E) by DEAE cellulose chromatography. Two of the major forms (B and C) have been further fractionated into two additional types (1 and 2) by countercurrent distribution. The purification of substrates A, C(1), and C(2) has been completed. Analysis shows that all three are glycoproteins with molecular weights of about 57,000, and have similar amino acid compositions. Differences exist in the sialic acid, glucosamine, and neutral hexose content, which may account for different physical properties. All the forms of the substrates are attacked by renin at similar rates, and appear to yield the same angiotensin I.

Amino Acids↗
PubMed1958

The synthesis of a tetradecapeptide renin substrate.

A tetradecapeptide renin substrate having a biological activity comparable to the natural product and similar chemical properties has been synthesized by means of the carbobenzyloxyl azide and mixed anhydride methods.

Angiotensinogen↗
PubMed1957

The preparation, purification, and amino acid sequence of a polypeptide renin substrate.

A purified preparation of a polypeptide renin substrate prepared by tryptic degradation of the protein renin substrate has been analyzed by the fluorodinitrobenzene method and after degradation with renin, carboxypeptidase, and phenylisothiocyanate, has been found to possess the amino acid sequence; asp-arg-val-tyr-ileu-his-pro-phe-his-leu-leu-val-tyr-ser. The first 10 of these amino acids constitutes hypertensin I which is released by cleavage of the leucyl-leucine bond by renin. The remaining 4 amino acids, leu, val, tyr, ser, apparently link hypertensin I to the protein renin substrate.

Amino Acid Sequence↗
PubMed1956

The amino acid composition of hypertensin II and its biochemical relationship to hypertensin I.

Preparations of hypertensin II, obtained from the treatment of hypertensin I by the action of the hypertensin converting enzyme of plasma and purified by countercurrent distribution, were quantitatively analyzed for their amino acid content. Chromatography on ion exchange columns showed the presence of equimolar amounts of aspartic acid, proline, valine, isoleucine, tyrosine, phenylalanine, histidine, and arginine. Hypertensin I was found to contain one mole of leucine and one mole of histidine in addition to the amino acids of hypertensin II. These two amino acids were isolated from the conversion products of hypertensin I and identified as the peptide histidylleucine. Carboxypeptidase digestion of hypertensin I showed the carboxyl terminal sequence of amino acids to be residue-phenylalanyl-histidylleucine. Similar studies of hypertensin II demonstrated residue-phenylalanine. It was concluded that the conversion of hypertensin I by the plasma hypertensin converting enzyme involved hydrolysis of the phenylalanyl-histidine bond to form hypertensin II and histidylleucine. The further removal by carboxypeptidase of phenylalanine from hypertensin II destroyed all of the vasoconstrictor activity.

Amino Acids↗
PubMed1956

The amino acid sequence of hypertensin. II.

The amino acid sequence of horse hypertensin II has been determined by the use of chymotrypsin, the fluorodinitrobenzene method, and stepwise phenylisothiocyanate degradation. The results indicate that the amino acids of hypertensin II are arranged in the following order: asp-arg-val-tyr-iso-hist-pro-phe.

Amino Acid Sequence↗
PubMed1956

The preparation and function of the hypertensin-converting enzyme.

It has been shown by use of isolated, perfused rat kidneys that hypertensin II is a potent vasoconstrictor substance while hypertensin I is not. Hence it would appear that in intact animals the pressor activity of hypertensin I results from its rapid conversion to hypertensin II. An enzyme which effects this conversion has been procured from horse plasma in a semipurified form by means of ammonium sulfate fractionation and isoelectric precipitation. A method is described for estimating the activity of the enzyme. An example of the use of the preparation in converting purified hypertensin I to hypertensin II has been described.

Angiotensin Amide↗
PubMed1956

The purification of hypertensin II.

The enzymatic conversion of hypertensin I to hypertensin II is described together with the subsequent purification of the product by means of counter-current distribution. Improved methods are also presented for the preparation of renin and its substrate, as well as in methods for the reaction of these materials and the purification of the resulting hypertensin I.

Angiotensin Amide↗
PubMed1955

Amino acid composition and electrophoretic properties of hypertensin I.

A preparation of hypertensin I was purified by countercurrent distribution and was shown to migrate as a single component in starch blocks at pH 9.3 and 4.2. It had an isoelectric point of 7.7. Quantitative analysis by ion exchange column chromatography showed eight amino acids in approximately unimolar proportion: aspartic, proline, valine, isoleucine, leucine, tyrosine, phenylalanine, and arginine. There were in addition two moles of histidine.

Amino Acids↗
PubMed1954

The purification of hypertensin I.

The purification of hypertensin I has been described. The final product which is four times as powerful a pressor agent as l-arterenol, is obtained with an over-all recovery of 40 per cent. The product consists of a single component in countercurrent distribution, having a nitrogen content of 15.97 per cent and a specific activity of 7050 Goldblatt units per mg. of N or 1125 units per mg. of solid. Acid hydrolysis and paper chromatography indicate in a preliminary fashion that there are about nine amino acids present in the intact polypeptide.

Amino Acids↗
PubMed1954

The existence of two forms of hypertensin.

Two types of hypertensin have been demonstrated by means of counter-current distribution. The first type is the product of the action of the enzyme, renin, upon its substrate and has been designated hypertensin I. It can be rapidly converted to a second approximately equally pressor compound, hypertensin II, apparently through the action of an enzyme in the plasma which requires halide or nitrate for activation. A highly purified preparation containing horse hypertensins I and II caused an elevation of blood pressure when injected into human beings.

Angiotensin Amide↗
PubMed1952

The isolation and assay of hypertensin from blood.

A method has been described for isolation and assay of hypertensin from the blood of dogs. An ethanol filtrate of blood drawn from the femoral artery is prepared and concentrated by evaporation. The hypertensin is extracted into n-butanol from which it is adsorbed into alumina, and subsequently eluted with dilute ethanol. The eluate is then evaporated to dryness, dissolved in water, and assayed by intravenous injection into rats.

Angiotensin Amide↗
PubMed1952

The assay of hypertensin from the arterial blood of normotensive and hypertensive human beings.

Hypertensin has been assayed in the blood of patients with normal blood pressure and in those with essential hypertension in both the benign and malignant phases. 250 ml. samples of arterial blood were obtained, chemically purified, and concentrated to a volume of 1 ml. These extracts were then assayed in anesthetized rats. The concentrations of hypertensin in the blood of patients with the malignant phase of essential hypertension were found to be greatly increased. The concentrations of hypertensin found in patients with benign hypertension had a moderate degree of overlapping with those found in the normotensive group, but the mean concentration of hypertensin in the former group was twice that of the controls. Although these results are statistically significant, the amounts of hypertensin recovered in the benign group are so small that no conclusions can be drawn as to its effectiveness in producing vasoconstriction in these patients.

Angiotensin Amide↗