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G Vaes

Publications and source records attributed to G Vaes.

77 records · Page 5Linked to original sources
PubMed1965

Studies on bone enzymes. The assay of acid hydrolases and other enzymes in bone tissue.

1. Nine acid hydrolases, cytochrome oxidase, alkaline phenylphosphatase and catalase were demonstrated in 0.25m-sucrose homogenates of newborn-rat calvaria. The acid hydrolases were: acid phenylphosphatase, acid beta-glycerophosphatase, beta-glucuronidase, beta-N-acetylglucosaminidase (beta-N-acetylaminodeoxyglucosidase), acid ribonuclease and acid deoxyribonuclease, showing optimum activity at about pH5; cathepsin, beta-galactosidase and hyaluronidase, with optimum activity at about pH3.6. 2. The main kinetic characters of these enzymes have been studied and methods for their quantitative assay have been worked out. The activities present in bone are given and compared with those found in liver. 3. Acid-phosphatase activity was assayed with phenyl phosphate and beta-glycerophosphate as substrates: activities with these two substrates appeared to be due to two different enzymes. Acid phenylphosphatase is particularly labile and is readily inactivated by various physical or chemical agents.

Journal Article↗
PubMed1965

Studies on bone enzymes. Distribution of acid hydrolases, alkaline phenylphosphatase, cytochrome oxidase and catalase in subcellular fraction of bone tissue homogenates.

1. When bone homogenates were fractionated according to the scheme developed for liver by de Duve, Pressman, Gianetto, Wattiaux & Appelmans (1955), all the enzymes assayed except cytochrome oxidase were found to occur partly in soluble and partly in particulate fractions. Among the particle-bound enzymes, the highest specific activity was found in the heavy-mitochondrial fraction for cytochrome oxidase, in the microsomal fraction for alkaline phenylphosphatase and in the light-mitochondrial fraction for eight acid hydrolases and for catalase. 2. Combined heavy-mitochondrial and light-mitochondrial fractions were subfractionated by isopycnic centrifugation in density gradients of sucrose or glycogen. In the various systems tried, cytochrome oxidase showed a relatively narrow distribution range with a sharp peak; the acid hydrolases and catalase showed flat and irregular distribution patterns, differing slightly in shape from one enzyme to the other. However, it was not possible to achieve a marked separation between the various enzymes under study. 3. It is concluded from these results that the acid hydrolases belong to special cytoplasmic particles, probably lysosomes, and that these particles are physically and enzymically heterogeneous. Catalase appears to be non-mitochondrial and could also belong to the lysosomes; but the possibility of an association with another type of particle must be kept in mind in view of what is known of liver catalase. Alkaline phenylphosphatase is largely attached to microsomal elements.

Journal Article↗
PubMed1965

Studies on bone enzymes. The activation and release of latent acid hydrolases and catalase in bone-tissue homogenates.

1. Eight distinct acid-hydrolase activities present in cytoplasmic extracts from bone tissue occur in latent form to the extent of 50-70% of their total activity, depending on the enzyme. 2. This latency can be decreased or suppressed by exposure to Triton X-100 or to media of low osmotic pressure, by treatment in the Waring Blendor, and by freezing and thawing, but not by increasing the substrate concentration in the assay medium up to 10-fold the Michaelis constant of the enzymes. 3. Latency is the property of the particle-bound enzymes, and treatments that suppress latency simultaneously cause solubilization of the enzymes. Most enzymes show an excess of free over soluble activity; the magnitude of this excess seems to depend largely on the nature of the enzyme, and sometimes also on the kind of treatment suffered by the preparations; it is attributed mainly to adsorption artifacts. 4. In preparations subjected to graded activating treatments, seven of the eight acid hydrolases studied are released in closely parallel fashion, suggesting that they are associated with particles possessing similar properties. Acid phenylphosphatase is released less readily than the other enzymes by Triton X-100 and by exposure to media of low osmotic pressure. 5. It is concluded from these and previous published fractionation experiments that, with the possible exception of part of the acid-phenylphosphatase activity, the eight acid hydrolases studied belong to lysosome-like particles. Bone lysosomes exhibit a relatively high degree of biochemical and physical heterogeneity. Their possible functions are discussed. Part of the acid-phenylphosphatase activity could be linked to another group of particles. 6. Catalase is also partly (30%) latent in cytoplasmic extracts of bone. Latent catalase can be released by some of the treatments that suppress the latency of the lysosomal enzymes, but differs from the latter by a greater resistance to Triton X-100, and, especially, by a complete insensitivity to exposure to media of low osmotic pressure. It is concluded from these results that the catalase-containing particles are probably different from lysosomes, as they are in liver. 7. Cytochrome oxidase, which is presumably associated with the mitochondria, and alkaline phenylphosphatase, an enzyme occurring predominantly in the microsomal fraction, exhibited no latency under the conditions of the present experiments.

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