Purine Ribonucleosidase g from Aspergillus foetidus

Nucleosidase g was prepared by growing Aspergillus foetidus on bran, and was purified by passage through a diethylaminoethyl-Sephadex column. The enzyme acted on the purine ribosides (except xanthosine) and on their 5'-phosphates. Action on the latter was a good means for preparing ribose-5-phosphate.     

Digestion by the larva of the pruinose scarab, Sericesthis geminata

An in vitro study of digestion by the subterranean larva of S. geminata revealed the presence of enzymes able to digest starch, trehalose, salicin, cellobiose, melibiose, maltose, sucrose, casein, and several forms of cellulose. The midgut is the major source of all enzymes except invertase and CMC-cellulase, for which hindgut preparations are more active. The pH values of the gut contents are: foregut 6.9, midgut 9.0 and hindgut 7.5. The midgut fluid is pumped forward into the foregut, and the carbohydrases in it are generally more active at the pH of the foregut than at the pH of the midgut. It is possible, therefore, that the foregut, which is itself insignificant as a source of enzymes, is the site of considerable carbohydrate digestion. The proteinase is inhibited 28% by trypsin inhibitors.

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Zusammenfassung Eine in vitro-Untersuchung über die Verdauungsvorgänge in den unterirdisch lebenden Larven von S. geminata wies Enzyme nach, die Stärke, Trehalose, Salicin, Cellobiose, Melibiose, Maltose, Rohrzucker, Kasein und mehrere Celluloseformen abbauen können. Versuche mit Vorder-, Mittel- und Enddarmextrakten zeigten, daß der Abbau von Rohrzucker und CMC-Cellulose in Ansätzen mit Enddarmpräparaten prozentual am höchsten war. Maximale Verdauung aller anderen geprüften Substrate erfolgte dagegen mit Mitteldarmpräparaten.Die pH-Werte betrugen im Vorderdarm 6,9, im Mitteldarm 9,0 und im Enddarm 7,5. Im Mittel- und Enddarm lagen die jewciligen optimalen pH-Werte für Maltose bei 6,5–7,0 und 7,5, für Melibiose bei 6,0–7,0 und 7,0–7,5, für Cellobiose bei 6,0–7,0 und 4,5, für Rohrzucker bei 7,0 und 6,0, für CMC bei 5,2 und 5,6.Die Verdauung unlöslicher Celluloseformen war durchweg gering, die der CMC dagegen beträchtlich.Die Mitteldarmflüssigkeit wird nach vorn in den Vorderdarm gepumpt. Die darin enthaltenen Carbohydrasen sind beim pH-Wert des Vorderdarmes meistens wirksamer als in dem des Mitteldarmes. Es ist deshalb möglich, daß im Vorderdarm, welcher selbst wahrscheinlich keine Enzyme produziert, doch eine beträchtliche Kohlenhydratverdauung stattfindet.Die Wirksamkeit der Proteinase wird durch bekannte Tryptin-Hemmstoffe um 28% reduziert.

     

THE RELATION BETWEEN THE INTRACELLULAR RIBONUCLEIC ACID DISTRIBUTION AND AMINO ACID INCORPORATION IN THE LIVER OF THE DEVELOPING CHICK EMBRYO

The RNA-P and DNA-P content of the nucleus and the RNA-P content of the whole cell of the livers of 8- to 20-day chick embryos and of adult fowls have been determined. The DNA-P content of the liver nuclei was slightly higher in the 8- and 10-day embryo than in all the other stages examined. A significant decrease in the RNA content of the cell occurred during embryonic development. The RNA content of the adult cell was the same as that of the 14- to 16-day embryo. The proportion of the cellular RNA contributed by the nucleus also decreased during development. In respect to both nuclear RNA content and distribution of RNA between nucleus and cytoplasm, the adult resembled the 8- to 12-day embryo. Examination of the fine structure of the cell showed that, as development progressed, free ribosomes decreased in number and the rough membranes increased. Slices of 8-, 14-, and 20-day embryonic livers and of adult livers were incubated with ¹⁴C-leucine, and the amount of labeled amino acid incorporated into whole tissue protein and into the proteins of the subcellular fractions was measured. Embryonic liver incorporated ¹⁴C-leucine 15 to 30 times more rapidly than adult liver. The microsomal protein was always more highly labelled than the protein in any other subcellular fraction; however, in the 8-day embryonic and the adult liver the proportion of total counts found in the nuclear fraction was considerably higher than in the 14- or 20-day embryonic liver. The significance of an apparent correlation between the proportion of the cell's RNA contributed by the nucleus and the proportion of total counts in the nuclear fraction is discussed.     

Effects of Triton X-100 on acid phosphatases with different substrate specificities

Summary The effect of Triton X-100 on the activities of acid phosphatases from wheat germ, potato and human prostate was tested using -glycerophosphate, p-nitro-phenyl phosphate and naphthol AS BI phosphate as substrates. There was little effect on -glycerophosphatase activity at the concentrations of Triton X-100 tested. However at low concen trations of the detergent there was a stimulation of the activities of p-nitrophenyl phosphatase and naphthol phosphatase which were inhibited with the higher concentrations. Triton X-100 was found to enhance colour production between naphthol AS BI and fast red violet LB.Further evidence is presented confirming the presence of more than one acid phosphatase from each of the sources employed.