Regulation information metabolism

Nearly all biological processes involve the specialized functions of one or more protein molecules. Proteins function to produce other proteins, control all aspects of cellular metabolism, regulate the movement of various molecular and ionic species across membranes, convert and store cellular energy, and carry out many other activities. Essentially all of the information required to initiate, conduct, and regulate each of these functions must be contained in... 

Information metabolism provides a way to store and retrieve the information that guides the development of cellular structure, communication, and regulation. Like other metabolic pathways, this process is highly regulated. Information is stored by the process of DNA replication and meiosis, in which we form our germ-line cells. These processes are limited to specific portions of the cell cycle. Information is retrieved by the transcription of DNA into RNA and the ultimate translation of the signals in the mRNA into protein. 

Regulation of information metabolism occurs at each stage. The net result is that specific proteins can be made when their activities are needed. 

Based on the accessibility of high-quality experimental information, we now focus on aspects of model interrogation and analysis. The question how cells actually control and distribute their flux under different conditions requires a mathematical and formal approach to metabolic regulation. The knowledge obtained by quantitative experiments must be, in the sense of Section II.B, encoded into a mathematical system, scrutinized utilizing the tools of formal analysis, and eventually decoded back into predictions about the natural system. 

Nucleic acids store and transmit genetic information and regulate metabolism in living cells. The genetic code is represented in the sequence of bases in the desoxyribonucleic add (DNA) helix (Fig. 10). 

Nucleosides play a vital role in many biological systems, not only as precursors to DNA and RNA but also in their own right, functioning as metabolic regulators. Consequently, the quantification and HPLC analysis of nucleosides in biological fluids can provide important information regarding their function. The analysis of the major and minor components of DNA and RNA is most conveniently carried out at the nucleoside level and will be considered as a separate section (Davis et al., 1979). 

The retinol transport system provides an interesting model for the study of protein-protein and protein-retinoid interactions and of the characteristics and metabolic regulation of a specific binding and transport system. The aim of this chapter is to summarize the information available about this transport system, including information about the structure and chemistry, biochemistry, and metabolism of RBP, and about related clinical phenomena. Brief comments are also... 

Any consideration of metabolic regulation must focus on those enzymes which exercise control over the flux of the pathway and the experimental means for identifying such enzymes. We have reviewed such experimental approaches, but we must now attempt to put the disparate pieces of information into some holistic approach. Kacser and Burns (1973) have questioned the general applicability of varying one factor at a time in trying to arrive at the importance of a particular factor in control and have developed instead an approach which attempts to interrelate the multiplicity of factors known to impinge on the flux of a pathway. The reader is directed to their paper for a full description of the theorem, including the mathematical manipulations involved in its application. 

It was our aim in this section of the chapter to present two of the methods presently used to determine the distribution of metabolites as examples of current approaches used in this area. It is important to be aware of the limitations of these approaches and to realize that a definitive method of localizing the concentration of small molecules within cells has yet to be devised. The data presently available, however, provide some insight into what is a recurring problem in metabolic regulation i.e., how to determine the concentration of a compound within a compartment of a functioning cell without so severely disrupting the cell that the information obtained is useless. 

Information concerning the metabolic function of unusual naturally occurring plant constituents might be used to develop new growth regulators. An example of a development that arose in this way began with the observation by Tolbert (143) that as much as 30% of the total soluble phosphorus in plant roots, and sometimes in the leaves,... 

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