Association of inorganic-pyrophosphatase activity with human alkaline-phosphatase preparations

1. The inorganic-pyrophosphatase activity of alkaline phosphatases prepared from human liver and small intestine was investigated at different stages of purification. 2. Both liver and intestinal preparations possessed pyrophosphatase activity at all stages of purification, and the two types of activity were not separated by gel filtration or by anion-exchange or cation-exchange chromatography. 3. After starch-gel electrophoresis of the tissue extracts, the zones of pyrophosphatase activity coincided exactly with alkaline-phosphatase zones. 4. Hydrolysis of each type of substrate was inhibited by the presence of the other, and a constant ratio of alkaline-phosphatase activity to pyrophosphatase activity was maintained during inactivation of the enzymes by incubation at 55 degrees . 5. These results are consistent with the view that alkaline phosphatases are also inorganic pyrophosphatases.

Changes in serum enzyme levels accompanying cardiac surgery with extracorporeal circulation

Serum lactic dehydrogenase, alpha-hydroxy-butyrate dehydrogenase, iso-citric dehydrogenase, and glutamic oxaloacetic transaminase activities were measured daily for two weeks postoperatively in the serum of 22 patients undergoing cardiac surgery with extracorporeal circulation.The length of perfusion was found to be a major factor affecting the extent of increased post-operative enzyme activities. Significantly higher levels were demonstrated in patients perfused for over one hour compared with those perfused for under one hour. Hepatocellular damage, age, and type of operation were not considered to be major factors in determining the extent of this increased activity.A considerable increase in enzyme activity was found to occur during perfusion when the dilution introduced by mixing the patient's circulation with the priming fluid of the heart-lung machine was taken into account. This dilution, when accounted for, increased the observed enzyme activity by 30 to 50%.

A comparison of aminoacyl-beta-naphthylamide hydrolases in extracts of human tissues

1. The aminoacyl-beta-naphthylamide-hydrolase activities of extracts of human liver, kidney, pancreas and small intestine were partially purified by chromatography on DEAE-Sephadex. 2. The enzymes from the different tissues showed slight variations in chromatographic behaviour and in mobility on starch-gel electrophoresis. 3. Michaelis constants for the hydrolysis of l-leucyl- and l-alanyl-beta-naphthylamide by the partially purified enzyme fractions were determined by a spectrofluorimetric assay method. The enzymes from different sources gave similar K(m) values. 4. l-Leucinamide and l-leucylglycine were competitive inhibitors of the hydrolysis of both substrates. Values of K(i) (leucinamide) and K(i) (leucylglycine) respectively were constant whatever combination of enzyme and substrate was used. 5. The relevance of these results to the identity or non-identity of the enzymes from different tissues is discussed.

Alteration in the electrophoretic mobility of alkaline phosphatases after treatment with neuraminidase

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Heterogeneity of liver alcohol dehydrogenase on starch-gel electrophoresis

1. Purified horse-liver alcohol dehydrogenase is heterogeneous on starch-gel electrophoresis in several buffer systems. 2. The electrophoretic pattern is altered by the addition to the buffers of oxidized or reduced coenzymes, isobutyramide, metal ions or metal-chelating agents. 3. The effect of coenzymes on the pattern suggests that the major cause of the observed heterogeneity is not the existence of isoenzymes, but the presence in the enzyme preparations of coenzyme-enzyme complexes or complexes with other nucleotides similar to, but less reactive than, the coenzymes. 4. Metal ions and chelating agents influence the electrophoretic separation by partial denaturation and inactivation of the enzyme.