Hinge movement

Instead of assuming a solid enzyme, in which active center the substrate molecule is bent (the concept of substrate strain), the idea was developed (Koshland 1958,1966) that enzymes can embrace the substrate molecule flexibly in the active center and effect reaction by the formation of specific interactions, the so-called induced jit . This picture is especially appropriate with allosterically activated enzymes or in situations in which part of the enzyme molecule has to turn or move over longer distances to effect catalysis (hinge movement), as for instance with most NAD(P)(H)-dependent enzymes (Stillman, 1999). 

Fig. 14. Nonrigid piping systems (a) three-hinge arrangement (b) free-movement arrangement.

For gas temperatures in excess of 380°C, experienced manufacturers often mount the adjustable guide vanes in special ceramic bearings. The shaft end of each blade is fixed to a lever, which is connected to a hinge-mounted adjusting cylinder. Axial movements of the cylinder open or close the blading. 

ADP. The hinge regions of myosin (referred to as flexible points at each end of S-2 in the legend to Figure 49-7) permit the large range of movement of S-1 and also allow S-1 to find actin filaments. 

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