INTERNAL EFFECTORS

The internal intermediates are B, C,D,..., and A and P are the respective initial substrate and final product. Within cells, the enzymes forming internal intermediates are rarely saturated with respect to the concentration of their individual substrates which are internal effectors of the pathway dynamics. 

As a consequence of penicillin interaction with the membrane of the cell, the pool level of an internal effector undergoes a slow change. The effector can be either an endogenous inducer, whose concentration rises as induction proceeds, or a co-repressor, whose falling concentration derepresses the penicillinase genes. Precursors to various cell-wall polymers are known to accumulate in S. aureus after exposure to penicillin [Park, 95-97 Ito and Saito, 98]. However, none of these compounds is a likely endogenous inducer within the cell, for similar compounds accumulate after treatment with other antibiotics which inhibit cell-wall synthesis (vancomycin, bacitracin) without induction of penicillinase. Penicillin-treated bacilli also do not appear to accumulate these compounds to the same extent as the staphylococci, though penicillinase induction follows. 

Next, the internal effectors of the flux, i.e., the concentrations S andP are expressed as functions of J by writing power approximations for those reactions which determine their concentrations in the regulatory sequence beginning with Ej, in this case... 

Figure 1.1 Functional components of the nervous system. The sensory division of the peripheral nervous system is sensitive to changes in the internal and external environment. The information gathered by this component is transmitted to the CNS where it is processed, integrated, and interpreted. The CNS then determines the appropriate response to this input. This response is carried out by the transmission of nerve impulses in the motor division of the peripheral nervous system to the effector tissues.

Ferrant, J.L. et al., The contribution of Fc effector mechanisms in the efficacy of anti-CD154 immunotherapy depends on the nature of immune challenge, Internal Immunol., 16, 1583, 2004. 

Figure 20.35 Mechanisms by which external or internal stress leads to cell damage resulting in apoptosis. The stress leads to activation of initiator proteolytic enzymes (caspases) that initiate activation of effector caspases. These enzymes cause proteolytic damage to the cytoskeleton, plasma membrane and DNA. The activation of DNAases in the nucleus results in cleavage of DNA chains between histones that produces a specific pattern of DNA damage which, upon electrophoresis, gives a specific pattern of DNA fragments. The major endproduct of apoptosis are the apoptolic bodies which are removed by the phagocytes.

A term applied to substances or agents that either depress or elevate the action of a particular catalyst. While often used synonymously with effector, the International Union of Biochemistry has suggested that the term modifier is more appropriate for those substances that are artificially added to in vitro systems. Other investigators restrict the use of the term modifier to those agents that eovalently modify the structure of the catalyst, thereby altering the catalyst s activity. See Effector Activator Inhibitor... 

It is regulated by the concerted action of the ability of the cell to respond to certain internal or external stimuli or the presence of the suitable effectors at the particular time. 

Caspase family. This scheme illustrates the domain structures, internal cleavage sites, preferred peptide substrate sequences, and biological function of caspases. Each procaspase consists of a large and small domain and may also possess DED (death effector domain) and CARD (caspase recruitment domain) (adapted from Hill etai, 2003). 

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