Mesoporous bioactive glasses as smart platform to stimulate bone regeneration

L'abstract è presente nell'allegato / the abstract is in the attachmen

A Simple Method for the Preparation of d-Ribulose 5-Phosphate

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Rose Bengal as a Specific Photosensitizer for a Histidine Residue at the Triphosphopyridine Nucleotide Binding Site of 6-Phosphogluconate Dehydrogenase

Rose Bengal is a potent inhibitor of 6-phosphogluconate dehydrogenase from Candida utilis and mediates the photoinactivation of the enzyme. The experiments reported in this paper indicate that photoinactivation occurs only when the dye is bound to the TPN binding site of the enzyme. Since the photoinactivation is correlated to the specific oxidation of only 2 residues of histidine, it can be assumed that this amino acid is located at the TPN binding site of 6-phosphogluconate dehydrogenase. These results are a new application of the technique of active site-specific photooxidation

Effect of orthophosphate on the transaldolase reaction.

In previous studies' with a dialyzed supernatant fraction from rat liver it was observed that the formation of heptulose phosphate from fructose g-phosphate was significantly inhibited by inorganic phosphate. It has since been shown (1, 2) that the activity of the dialyzed liver fraction can be related to its content of transketolase and transaldolase and it became of interest to determine whether the inhibition of the over-all process by phosphate was due to its effect on one or both of the enzymes involved in this process. Preliminary experiments indicated that both transketolase and transaldolase were inhibited by inorganic phosphate when the enzymes were tested in the usual assay procedures. The effect of phosphate on transaldolase is reported in the present paper

THE NATURE OF THE AMINO ACID RESIDUES INVOLVED IN THE INACTIVATION OF GLUCONATE 6-PHOSPHATE DEHYDROGENASE BY IODOACETATE.

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Fructose 1,6-Diphosphatase from Rabbit Liver XII. EFFECT OF SUBSTRATE AND ADENOSINE MONOPHOSPHATE ON THE IONIZATION OF THE TYROSYL RESIDUES

Abstract The effects of substrate and AMP on the state of ionization of tyrosyl residues of fructose 1,6-diphosphatase have been investigated. In the native enzyme, 5 to 6 tyrosyl residues were titrated with a pK of about 8.4, and 7 to 8 residues were titrated with a pK of 9 to 9.2. The remaining tyrosyl residues were not titrated below pH 10. In the presence of 10-5 m fructose 1,6-diphosphate, when 4 moles of substrate are bound per mole of enzyme, approximately 4 of the low pK tyrosyl residues are shifted from pK 8.4 to pK 9.7. However, all of the pK values are modified, and under these conditions 2 tyrosyl residues show a pK of 8.7, and 10 or 11 residues show a pK of 9.7. At a high concentration of fructose 1,6-diphosphate, 10-3 m, all 12 to 13 of the tyrosyl residues are titrated with a pK of 9.8. The results can be correlated with previous studies on the acetylation of fructose 1,6-diphosphatase. The tyrosyl residues with low pK are more reactive and are associated with loss of sensitivity to AMP. However, after acetylation, only 10 tyrosyl residues are titrated with a pK of 9.3 to 9.4, and the pK is shifted to 9.7 when the substrate is bound. A method of analyzing the titration data is presented which permits simultaneous evaluation of number of residues and pK value of each titrated group. This has revealed changes in tyrosyl residues that would otherwise have been overlooked

Studies on the mechanism of action of the gluconate 6-phosphate dehydrogenase. The presence of a cysteine residue in the active center.

Abstract The role of the sulfhydryl groups in the gluconate 6-phosphate dehydrogenase has been studied. Nine cysteine residues have been detected by spectrophotometric titration with p-hydroxymercuribenzoate, but the reaction of only 3 of them is sufficient to inactivate the enzyme completely. Chlorodinitrobenzene acts even more specifically. Incorporation of 1.6 dinitrobenzene residues leads to enzyme inactivation. The amino acid residues involved in dinitrophenylation have been identified as cysteine. Gluconate 6-phosphate completely protects the enzyme against inactivation by chlorodinitrobenzene

Molecular and Functional Properties of a Calpain Activator Protein Specific for μ-Isoforms

A natural calpain activator protein has been isolated from bovine brain and characterized in its properties and molecular structure. The protein is a homodimer with a molecular mass of about 30 kDa and results in being almost identical to UK114 goat liver protein. Significant similarities with mouse HR12 protein were also observed, whereas a lower degree of similarity was found with a family of heat-responsive proteins named YJGF and YABJ from Haemophilus influenzae and Bacillus subtilis, respectively. The brain activator expresses a strict specificity for the mu-calpain isoform, being completely ineffective on the m-calpain form. As expected, also UK114 was found to possess calpain-activating properties, indistinguishable from those of bovine brain activator. A protein showing the same calpain-activating activity has been also isolated from human red cells, indicating that this factor is widely expressed. All these activators are efficient on mu-calpain independently from the source of the proteinase. The high degree of specificity of the calpain activator for a single calpain isoform may be relevant for the understanding of sophisticated intracellular mechanisms underlying intracellular proteolysis. These data are indicating the existence of a new component of the Ca2+-dependent proteolytic system, constituted of members of a chaperonin-like protein family and capable of promoting intracellular calpain activation