Rat-Liver Phosphatases

Goodlad, George Alexander James (1954) Rat-Liver Phosphatases. PhD thesis, University of Glasgow.

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Abstract

1. pH-activity curves have been determined for the phosphatase activity of rat liver homogenates using as substrates, alpha- and beta-glycerophosphate, phenyl phosphate, p-nitrophenyl phosphate, adenosine-3'-phosphate, adenosine-5'-phosphate, inosine-5'-phosphate, glucose-1-phosphate and glucose-6-phosphate. The effect of Mg ions on these curves was also studied. Evidence was obtained from these studies which indicated the presence in liver of three non-specific acid phosphatases, a non-specific alkaline phosphatase, specific 5'-nucleotidase and glucose-6-phosphatase activity. 2. The intracellular distribution of these enzymes was studied using the differential centrifugation methods of Schneider (1948) and Hogeboom, Schneider and Striebich (1952). Alkaline phosphatase and 5'-nucleotidase were the only enzymes found in significant amounts in the nucleus. Non-specific acid phosphatase activity was present in large amounts in the mitochondria and to a lesser extent in the microsomes. The microsomal fraction contained large amounts of glucose-6-phosphatase activity and 5'-nucleotidase activity. More than 50% of the alkaline phosphatase activity was found in the non-particulate cytoplasm. 3. The effect of various inhibitors and activators on the acid phosphatase activity of rat liver homogenates was studied over a wide pH range and the results confirmed for the existence of at least two acid phosphatases. 4. Further evidence for the existence of two acid phosphatases was obtained from fractionation studies involving acetone precipitation in the presence of Zn++ ions and electrophoresis in the Tiselius apparatus. 5. The alkaline phosphatase activity of nuclear and cytoplasmic fractions was further studied in normal and regenerating rat livers, and from the effect of pH and Mg++ ions it was concluded that two enzymes were probably present in the cytoplasm and only one in the nucleus. The presence of two alkaline phosphatases in the cytoplasm was also suggested from determinations of the activation energy at different pHs. Fractionation and electrophoretic studies, however, failed to indicate the presence of more than one alkaline phosphatase. 6. The hydrolysis of glucose-1-phosphate by whole tissue extracts and intracellular fractions was studied along with some of the properties of liver phosphoglucomutase. The results indicate that the mechanism of hydrolysis of G-1-P is by a two stage process involving a preliminary conversion to glucose-6-PO4 and subsequent hydrolysis of this compound by glucose-6-phosphatase. No evidence for any secondary pathway was obtained.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Biochemistry
Date of Award: 1954
Depositing User: Enlighten Team
Unique ID: glathesis:1954-79140
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 11:39
Last Modified: 05 Mar 2020 11:39
URI: http://theses.gla.ac.uk/id/eprint/79140

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