Kinji Tsukada

Polynucleotide ligase from rat liver after partial hepatectomy.

Abstract Polynucleotide ligase, which catalyzes the covalent joining of two segments of an interrupted strand in a DNA duplex, was extracted from rat liver. The activity is located in both nuclei and soluble fractions. Its optimal pH was 8.0. The enzyme requires ATP as a cofactor. Its activity was completely dependent on the presence of Mg 2+ . The activities of these enzymes in regenerating rat liver were 4 times higher, in both fractions, than those in normal rat livers.

Two distinct polynucleotide ligases from rat liver.

Polynucleotide ligase has been shown to be present in both soluble and nuclear fractions from rat liver [ 1,2], and the activities of these enzymes are increased in relation to the rise of DNA synthesis after partial hepatectomy [3]. With a view to studying the function of these ligases in regenerating rat liver, we have tried initially to purify and characterize them from both fractions of normal liver. During the course of these studies, Zimmerman and Levin [4] have described the properties of purified polynucleotide ligase from nuclei of rat liver. The purpose of this report is to present evidence that the ligase from the soluble fraction is a distinguishable species from that of the nuclear fraction.

Activity of serum ribonuclease after partial hepatectomy and acute stress in the rat

Abstract Partial hepatectomy and acute stress (intraperitoneal injection of Celite) caused a decrease in the activity of serum ribonuclease. The decrease in activity after partial hepatectomy differed kinetically from that after acute stress. The decreased activity of serum ribonuclease was closely related to an increase in the level of ribonuclease inhibitor in the serum.

Changes in polynucleotide ligase during rat liver regeneration

Abstract The specific activity of polynucleotide ligase in rat liver seems to begin to rise at 16 hours after partial hepatectomy (removal of 70% of the liver). The increases reach their maxima about 24 hours after operation, rising to at least 4 to 5 fold normal levels. Cycloheximide caused a decline in the increased activity of polynucleotide ligase. Since the specific activity of the ligase of normal rats is very little affected by cycloheximide, the possibility is considered that the newly formed enzyme is different from the one normally present in liver.

Rat serum ribonuclease

Abstract Rat serum ribonuclease has been purified about 6000-fold. The optimal pH of this enzyme was 7–8. The purified enzyme was rather heat labile at pH 7.6. The Km of this enzyme is 30% higher than that of the crystalline bovine pancreatic ribonuclease (polyribonucleotide 2-oligonucleotide-transferase, EC 2.7.7.16). No stimulatory or inhibitory effect on this enzyme was observed with EDTA, KCl, MgCl2. p-chloromercuribenzoinc acid, or mercaptoethanol.

Protein kinase in cultured plant cells

A protein kinase (EC 2.7.1.37) which phosphorylates histones was purified partially from the soluble fractions of cultured plant cells. The optimum pH was 7.5 to 9.0. The activity wasnot stimulated by exogeneous cyclic AMP. It was thermolabile and completely dependent on the presence of Mg2+ or Mn2+ for activity. p-Chloromercuribenzoate inactivated this enzyme and this inactivation was overcome by mercaptoethanol.

Adaptive response of tryptophan pyrrolase and tyrosine transaminase in rat liver after partial hepatectomy and laparotomy

Abstract Tryptophan pyrrolase ( L -tryptophan: H 2 O 2 oxidoreductase, EC 1.11.1.4) and tyrosine-α-ketoglutarate transaminase ( L -tyrosine: 2-oxoglutarate amino transferase, EC 2.6.1.5) activities of rat liver homogenate were increased about 2–2.5 fold in 4–6 h after laparotomy, and 4–6 fold in 8–10 h after partial hepatectomy, without loading of gluccorticoid or substrate. The rise of tryptophan pyrrolase was inhibited by actinomycin D administered immediately after operation. In adrenalectomized rats, the induced tryptophan pyrrolase activity was inhibited. The increased activity in tryptophan pyrrolase after partial hepatectomy has been attributed to change in supernatant fraction, and was not affected by administration of cortisone.

Polyribosomes in antibody-forming tissues of hyperimmunized rabbits

Abstract 1. 1. Lymph nodes of hyperimmunized rabbits have been found to contain polyribosomes which are dissociated into monomers by ribonuclease. 2. 2. By means of an enzyme-antienzyme system, specific inhibition of bacterial α-amylase activity with these ribosomal fractions has been observed.

Studies on the function of deoxyribonuclease inhibitor after partial hepatectomy

Abstract Partial hepatectomy and acute stress (intraperitoneal injection of celite) caused an increase in the activity of serum deoxyribonuclease inhibitor. The increased activity after partial hepatectomy differed kinetically from that after acute stress. Deoxyribonuclease inhibitor was purified from rat liver about 30-fold and its properties were studied and found to be those of a protein. The activity of the inhibitor in rat liver increased after partial hepatectomy. The activity of the inhibitor may not be related to the activity of DNA synthesis as assayed by the incorporation of [ 3 H]thymidine.