The fine localization of nucleoside triphosphatase activity in the retina of the frog

Nucleoside triphosphatase (NTPase) activity was demonstrated at the submicroscopic level in the frog retina by the Wachstein-Meisel method utilizing various purine and pyrimidine nucleosides. Under the electron microscope magnesium-activated NTPase was localized in the outer and inner segments, and in the plexiform layers. NTPase active sites in the cones were localized diffusely in the 70 to 80 A interspaces between the double membranes of the stacked lamellae and in the investing cytoplasm. In the rods, on the other hand, sites of activity were observed at the periphery of the stacked lamellae as discrete electron opaque deposits measuring 1000 to 1500 A which interdigitated between the lamellae for short distances. Deposits of reaction product appeared more numerous in rods of dark-adapted frogs stimulated with monochromatic light with a wave length of 510 mmicro. Enzyme activity was also observed in mitochondria of the rod and cone ellipsoids. In the outer and inner plexiform layers NTPase active sites were present on and between the membranes of axons and the plasma membranes of some of the neurons.

Metabolism in infection: study on the enzymatic damage in kidney of guinea pig infected with Mycobacterium tuberculosis

Malic dehydrogenase activity of the kidney homogenate from the normal and the tuberculous guinea pigs has been estimated. A defect in the electron transport chain has been detected at the level of flavoprotein-diaphorase system. A significantly high DPNase activity of kidney homogenate has also been found in the infected group. Niacin and phenazine methochloride could correct both the defects and improve the tetrazolium reduction of the homogenate in the infected group to the level of the normal activity. Oxidative phosphorylation by the kidney mitochondria from the tuberculous guinea pigs was found to be low and could not be improved by niacin and phenazine methochloride, unlike their effects on the reduction of tetrazolium. Results have been discussed in the light of the over-all intercellular economy and its relation to the symptom complexes in tuberculosis.

SPECIFICITY OF POTASSIUM-ACTIVATED PHOSPHODIESTERASE OF ESCHERICHIA COLI

A potassium-activated phosphodiesterase that hydrolyzes polyribonucleotides to 5'-mononucleotides has been purified approximately 600-fold from extracts of Escherichia coli B. The purified enzyme appears to be specific for single-stranded polyribonucleotides: helical forms are not hydrolyzed, nor do they inhibit the hydrolysis of single-stranded chains.

BACTERIAL NUCLEOTIDASES

Kohn, J. (Queen Mary's Hospital, London, England) and J. L. Reis. Bacterial nucleotidases. J. Bacteriol. 86:713-716. 1963.-The 3- and 5- nucleotidase activity in various bacterial species was investigated. Both enzymes were found in bacterial extracts in varying proportions. The nucleotidases were found to be very active in Proteus vulgaris, in which organism they were studied in detail. The relative activities, the pH optima, and the effect of metal ions were investigated. It was concluded that bacterial 3- and 5-nucleotidases are distinct and separate enzymes.

ENZYME HISTOCHEMISTRY OF INDUCED AND TRANSPLANTED SQUAMOUS CELL CARCINOMA OF THE UTERINE CERVIX

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EVIDENCE FOR EXTRACELLULAR ENZYMIC ACTIVITY OF THE ISOLATED PERFUSED RAT HEART

1. The dissimilation of a number of externally added hexose phosphates and 5'-nucleotides by the perfused rat heart is described, and non-specific esterase and 5'-nucleotidase activity associated with the superficial cell membrane or vascular system has been demonstrated. 2. The rate of production of (14)CO(2) from [U-(14)C]glucose 6-phosphate suggests that oxidation occurred after hydrolysis to glucose. The incorporation of isotope from [U-(14)C]glucose 6-phosphate into glycogen was small, and similar to that obtained with [U-(14)C]glucose as substrate. 3. Glucose 6-phosphate was also partially isomerized to fructose 6-phosphate. Similarly, fructose 6-phosphate was converted mainly into glucose 6-phosphate, but also into glucose and inorganic phosphate. When fructose 1,6-diphosphate was added to the perfusate, a mixture of glucose 6-phosphate, fructose 6-phosphate and triose phosphates accumulated in the medium approximately in the equilibrium proportions of the phosphohexose-isomerase and triose phosphate-isomerase reactions, together with inorganic phosphate and some glucose. Glucose 1-phosphate was hydrolysed to glucose, but was not converted into glucose 6-phosphate. Leakage of enzymes out into the perfusion fluid did not occur. 4. This demonstration that phosphohexose isomerase, triose phosphate isomerase and aldolase may react with extracellular substrates at an appreciable rate suggests that these enzymes are attached to the cell membrane.

STUDIES ON NECROSIS OF MOUSE LIVER IN VITRO: ALTERATIONS IN SOME HISTOCHEMICALLY DEMONSTRABLE HEPATOCELLULAR ENZYMES

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SOME CHARACTERISTICS OF STREPTOCOCCAL NICOTINAMIDE ADENINE DINUCLEOTIDASE AND STREPTOLYSIN O

Pentz, E. Irene (Northwestern University School of Medicine, Chicago, Ill.), Eva Kot, and J. J. Ferretti. Some characteristics of streptococcal nicotinamide adenine dinucleotidase and streptolysin O. J. Bacteriol. 88:497-508. 1964.-Nicotinamide adenine dinucleotidase produced by Streptococcus pyogenes strain C203U, grown in Todd-Hewitt broth (Difco), was recovered from diethylaminoethyl-cellulose columns free from streptolysin O. It contained a trace of deoxyribonuclease. The elution peak of nicotinamide adenine dinucleotidase was fairly symmetrical; when it was treated with dinitrofluorobenzene (DNFB) and chromatogrammed on paper in three different solvent systems, only one yellow spot was obtained. Examination of the enzyme in an ultracentrifuge presented no moving boundary. The pore size of two different widths of Visking casing was estimated by dialyzing proteins or peptides of known molecular weight and testing the dialysate for their appearance. The casing which allowed a molecule of 2,500 molecular weight to pass, but not one of 3,000 molecular weight, retained the nicotinamide adenine dinucleotidase. A fragment having no nicotinamide adenine dinucleotidase activity did pass through this casing, however, but was retained by the second casing which retained molecules weighing 2,500. Amino acid analyses of three different nicotinamide adenine dinucleotidase preparations were remarkably similar, and were characterized by a high content of proline and glycine and a very low content of sulfur-containing amino acids. Examination by treatment with DNFB followed by hydrolysis for the presence of N-terminal amino acids ruled out all amino acids, with the possible exception of arginine. The combined evidence suggests that its molecular weight is between 2,500 and 20,000. Some data are presented to illustrate the irreversible instability of streptolysin O; amino acid analyses for three separate preparations of high activity indicate a very low content of sulfur-containing amino acids.