Cyclic nucleotide phosphodiesterase from wheat sprouts. Purification, properties, effect of systemic fungicides

Cyclic nucleotide phosphodiesterase from wheat sprouts was isolated and partially purified. The molecular weight of the enzyme is about 83 000. The enzyme activity sharply rises as the inhibiting factors present in the homogenate are separated. The pH optimum of the enzymatic reaction is 4,8. Divalent cations (Mg2+, Mn2+, Cu2+) within the concentration range of 1--5 mM and complexons (EDTA, EGTA) at the concentration of 1 mM do not affect the PDE activity. The temperature optimum for the reaction is 60 degrees. The enzyme hydrolyzes 3' : 5'-AMP, 3' : 5'-GMP and 2':3'-AMP. The Km value for cAMP is 4 . 10(-3) M. The enzyme activity is inhibited by chemical agents possessing the fungicide activity, the strongest effect being exerted by anylate.     

Monooxygenase activity of human hemoglobin: role of quaternary structure in the preponderant activity of the beta subunits within the tetramer

Catalysis of para hydroxylation of aniline was measured for human ferrihemoglobin and various derivatives in a reconstituted system consisting of the appropriate hemoprotein (at 4 microM heme), reduced nicotinamide adenine dinucleotide phosphate (NADPH), cytochrome P-450 reductase, and aniline under atmospheric O2. The isolated subunits of hemoglobin (alpha 3+ and beta 3+4) were prepared by treatment with p-(hydroxymercuri)benzoate. Semihemoglobin (alpha heme2 beta 02) was prepared from ferrihemoglobin and apohemoglobin. Converse valency hybrids alpha 3+2(beta 2+-CO)2 and (alpha 2+-CO)2 beta 3+2 were prepared from appropriately ligated alpha and beta subunits. After chromatography, the hemoglobin derivatives were characterized by visible and 1H NMR spectroscopy and electrophoresis. At the same concentration of aniline, the alpha and beta subunits were much less active than the normal tetramer. alpha-Semihemoglobin and the alpha 3+2(beta 2+-CO)2 hybrid also displayed lower hydroxylase activity. The (alpha 2+-CO)2 beta 3+2 hybrid was about as active as normal alpha 3+2 beta 3+2. This result suggests that the activity of tetrameric hemoglobin primarily involves the beta subunits. Also transfer of the beta subunits from the beta 4 molecular environment to the alpha 2 beta 2 state enhances their monooxygenase activity approximately 15-fold. The hemoglobin derivatives were differently susceptible to substrate inhibition, the beta 4 species being most sensitive. Estimates of Vmax from the linear portions of the corresponding Lineweaver-Burk plots showed agreement within a factor of 2.5 for all of the hemoglobin derivatives, suggesting that the intrinsic O2-activating capacities of the derivatives are similar.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mitochondrial DNA in Xenopus laevis oocytes. I. Displacement loop occurrence

Displacement loops are found in mitochondrial DNA isolated from the ovaries of mature female Xenopus laevis. These displacement loops subtend some 7% of the contour length of a mitochondrial circular DNA. When mature oocytes are shed as unfertilized eggs at least 76% of the mitochondrial DNA in these eggs contains displacement loops. The implications of these findings are discussed with respect to displacement loop occurrence in other mitochondrial DNAs and especially with respect to mitochondrial DNA replication.     

Biochemical applications of a synchronously pumped krypton ion dye laser fluorescence system.

A synchronously pumped krypton ion dye laser fluorescence system is shown to provide tunable, polarized, subnanosecond pulses at high repetition rates, modest peak powers, and low energy. Such a source is uniquely suited to fluorescence investigations of biochemical mechanisms. Applications of this fluorescence excitation source to analysis, life-time determination, and depolarization effects are discussed.     

Comparison of whole-cell protein electrophoretic profiles of Haemophilus influenzae: implementation of a microcomputer mainframe linked system and description of a new similarity coefficient

A microcomputer mainframe linked system is described which allows video camera data capture and storage of one-dimensional whole-cell protein electrophoresis gel images, processing of normalized traces to produce a similarity matrix, and analysis of the matrix using the commercial cluster analysis program CLUSTAN. A new similarity coefficient is introduced which takes into account both band position and intensity. Forty-five strains of Haemophilus influenzae, including the eight biotypes and six serotypes, were analyzed using this system. Results demonstrated groupings which are consistent with known genetic relationships.     

Nile crocodiles, Crocodylus niloticus, and estuarine crocodiles, Crocodylus porosus, show similar osmoregulatory responses on exposure to seawater

1. Nile crocodiles, reared in fresh water and exposed acutely to seawater, suffer marked dehydration and hypernatraemia. Cloacal urine osmolarity and potassium concentration increased markedly but urine sodium remains low. 2. Hypernatraemia is increased when secretion from the lingual salt glands is prevented. 3. C. niloticus appears not to drink seawater. 4. Similarities in osmoregulatory response between estuarine and Nile crocodiles suggest that the lingual salt glands of C. niloticus are functional in salt water, playing an important role in sodium balance. 5. Significant differences in the function of the renal/cloacal complex of Alligator and Crocodylus emphasize further the differences between these two groups of crocodilian and provide support for the postulated marine ancestry of many or all of the Crocodylidae.