John S. Heller

The appearance of an ornithine decarboxylase inhibitory protein upon the addition of putrescine to cell cultures

Quiescent, contact inhibited H-35 rat hepatoma cell cultures maintained in minimal essential medium contain a very low level of ornithine decarboxylase activity. However, 2 h after the addition of 10% fetal calf serum to the culture medium, the enzyme activity increases by approx. 100-fold. This increase can be completely inhibited by the simultaneous addition of 10(-2) M putrescine. The presence of putrescine elicits the appearance of an intracellular inhibitor of ornithine decarboxylase. This inhibitor of ornithine decarboxylase has a molecular weight of 26500, is sensitive to the action of chymotrypsin and is noncompetitive with respect to ornithine. The intracellular appearance of this inhibitor is sensitive to cycloheximide but is only partially inhibited by actinomycin D.

The regulation and function of ornithine decarboxylase and of the polyamines.

Publisher Summary This chapter highlights the regulation and function of ornithine decarboxylase (ODC) and of the polyamines. ODC catalyzes the synthesis of putrescine. It is necessary to distinguish among several possible functions of polyamines, to define the state of the cell at the time of induction, and to differentiate among various modes of induction of ODC activity. The chapter discusses a few new aspects of the regulation and function of ODC and of the polyamines and some of the uncertainties in the field. It also presents areas that are closely related to the regulation and the interrelationships of the polyamines in a variety of physiological and pathological states. The chapter also explores the possible functions of the polyamines.

Studies on the regulation of ornithine decar☐ylase activity by the microtubules: The effect of colchicine and vinblastine

Abstract Colchicine and vinblastine in micromolar concentrations inhibit the activity of ornithine decar☐ylase (E.C.4.1.1.17) (ODC), of mouse leukemia L1210 cells, which has been stimulated by dilution of the cells with fresh medium and serum. The colchicine analogues, lumicolchicine and colchiceine, which do not affect microtubular strcuture, do not inhibit ODC activity even at 10 −4 M. However, it appears that disruption of the microtubular structure is not in itself enough to inhibit ODC activity but that one or more additional temperature dependent steps are involved. We propose that the microtubule system is one of a series of components which regulates ODC activity.

Localization of glutamic acid decarboxylase within laminae of the rat olfactory tubercle.

—There are three histological layers within the rat olfactory tubercle: plexiform, pyramidal and polymorphic. We have assayed glutamic acid decarboxylase (GAD) and GABA in homogenates of frozen sections cut parallel to these layers. Consecutive sections (16 μm) were homogenized in groups and assayed for GAD or GABA. Every seventh section was stained with Toluidine Blue to monitor the depth and orientation of the plane of section. Steep variations in GAD activity (up to 6‐fold) were observed as a function of depth in the tubercle. These were paralleled by corresponding but less marked variations in GABA levels. The lowest values were found in the plexiform layer. This suggests that GAD may play a very limited role there. The highest activities were found in sections from the deepest lamina of the polymorphic layer. This is the only lamina of the tubercle that does not receive a dopaminergic input.

The inhibition of the induction of ornithine decarboxylase by cations

Abstract L1210 cells reinitiate growth after dilution with fresh medium; during this time there occurs a transient increase in ornithine decarboxylase (EC4.1.1.17) (ODC) activity. The addition of 10 to 20 mM Na+, K+ or Mg++ completely inhibits this induction of ODC activity with no effect on cell growth. These cations also inhibit the increase of ODC activity in neuroblastoma cells and in H-35 cells which is induced by prostaglandin E1 plus 3-isobutyl-1-methyl-xanthine and by 15% fetal calf serum respectively. This inhibitory effect of low levels of cations on the induction of ODC activity in different cell lines suggests that the intracellular function of ODC, and of the products of the reaction it catalyzes (putrescine, spermidine and spermine), may be intimately involved with changes in cation pools.

Purification and properties of the antizymes of Escherichia coli to ornithine decarboxylase

The purification of the antizymes to ornithine decarboxylase of Escherichia coli to homogeneity is detailed. An acidic component, pI 3.8, and two basic histone-like proteins, pI above 9.5, are described. The two latter proteins constitute approximately 90% of the total antizyme activity.