Interactions between glycolytic enzymes and components of the cytomatrix.

Abstract

Evidence is provided that enzymes absorb to cellular structures in a wide range of tissues . In particular, the interactions between glycolytic enzymes and the microfilaments of the cytoplasm are described . The relevance of these interactions to the compartmentation of carbohydrate metabolism is discussed . Examples are given of the variations in degree of binding during alteration of tissue metabolism and, for individual glycolytic enzymes, during fetal development and differentiation . Overall, these data support the concept that metabolic activities in the cytoplasm have an organized structure . just as the structural elements of the cytosolic compartment have evolved with the capacity to assemble and disassemble in response to the changing requirements of the organism, so the metabolic elements appear to have evolved a parallel system that provides for the appropriate positioning of an energyproducing sequence in relation to the specific, dynamic requirements of the cytoskeleton .In other papers in this supplement there are many fascinating examples of the structural role of the cytomatrix and of the phenomena of directed motion in relation to this complex spatial organization. Cell shape, motility, cytoplasmic streaming, organelle distribution, cell division, and differentiation have all been viewed from this perspective, and the data leave little doubt as to the extraordinarily broad involvement of the cytomatrical structure (16) . At a functional level, the intricate choreography of structural reorganization during these cellular processes clearly requires an appropriate energy source, one with several special features. In this paper I describe the characteristics of the interactions between the glycolytic enzymes and the components of the cytomatrix, characteristics that may be of particular relevance in this context . Enzyme Binding and CompartmentationRecent studies (11, 12, 18) on intermediary metabolism have focused on the importance of compartmentation in the regulation of cellular processes and, to quote a recent treatise on this topic . ... . . it has become overtly clear that, in biology, order in metabolism is generated by the introduction of inhomogeneity, i.e., by compartmentation" (18).To most cell biologists, the most familiar examples of the metabolic advantages of the segregation of enzymes and metabolites are associated with compartmentation of cells and subcellular organelles, where a particular metabolic organization is surrounded and separated from other metabolic compartments by a physical permeability barrier, such as a 2225 membrane. Although this type of spatial compartmentation is undoubtedly the most intensively studied at this time, it is important to stress that effective metabolic compartmentation may also be achieved within a single membrane-enclosed space by means of the binding of key enzymes and metabolites. Thus, in the case of the cytoplasmic matrix, compartmentation by binding of soluble enzymes to the matrical structures may confer advantages over and above t...

Axonal transport of the cytoplasmic matrix.

“…A stably polymerized form of actin has been identified in the axon (48). Furthermore, microfilaments bind many different cytoplasmic proteins, including metabolic enzymes such as aldolase, with relatively high affinity (41). Thus, microfilaments could provide a large number of sites for binding other SCb proteins to the carrier structure .…”

Proteomic characterization of harvested pseudopodia with differential gel electrophoresis and specific antibodies

“…Numerous studies have demonstrated interactions between the cytoskeleton and glycolytic enzymes, especially GAPDH, aldolase and PK. [25][26][27][28][29][30][31][32][33][34][35][36][37][38] In this study, quantities of these glycolytic enzymes, as well as actin, tubulin and tropomyosin, were sufficient in U87 pseudopodia to be detected with Figure 4 DeCyder ratios Coomassie blue staining, thus establishing the potential for the energy-generating portion of the glycolytic pathway to energize cytoskeletal proteins for migration within U87 pseudopodia. Polymerization of actin and tubulin shares a similar use of energy from nucleotide triphosphate hydrolysis.…”

Aldolase exists in both the fluid and solid phases of cytoplasm [published erratum appears in J Cell Biol 1988 Dec;107(6 Pt 1):following 2463]

“…This work suggested that previously reported "glycolytic component" complexes (13,14,34) were actually complexes of glycolytic enzymes with structural proteins, and implied that the glycolytic particle might exist as such a complex. The model for the cytoplasmic organization of glycolytic enzymes that has emerged from Clarke and Masters' work is that there is a "plating" of glycolytic enzymes around the filamentous actin (F-actin) ~ core of microfilaments (48). Masters proposed a dynamic three-way equilibrium among monomeric actin, F-actin, and glycolytic enzymes, resulting in a microdomain of glycolytic enzymes surrounding actin filaments.…”