Current Topics in Cellular Regulation, Volume 20 evaluates the basic mechanisms involved in the regulation of diverse cellular activities. This book discusses the role of glutamine in the flow of nitrogen, regulation of glycogen synthase activity by covalent phosphorylation, and physiological role of PFK phosphorylation. The in vivo modulation of HMG-CoA reductase activity, hypotheses on the role of eIF-2 phosphorylation, and ADP-ribosyltransferase from turkey erythrocytes are also elaborated. This text likewise covers the non-enzymic effects of vanadate and phosphorylation of liver and muscle PFK. This volume is a good source for biologists and researchers interested in advances in the general area of cellular regulation.