Next page enzyme structure

Lactate dehydrogenase (LDH, EC 1AA.27) is discussed in some detail here and on the next page as an example of the structure and function of an enzyme. 

The active center of an LDH subunit is shown schematically in Fig. 2. The peptide backbone is shown as a light blue tube. Also shown are the substrate lactate (red), the coenzyme NAD (yellow), and three amino acid side chains (Arg-109, Arg-171, and His-195 green), which are directly involved in the catalysis. A peptide loop (pink) formed by amino acid residues 98-111 is also shown. In the absence of substrate and coenzyme, this partial structure is open and allows access to the substrate binding site (not shown). In the enzyme lactate NAD"" complex shown, the peptide loop closes the active center. The catalytic cycle of lactate dehydrogenase is discussed on the next page. 

Reactions quite analogous to the enzyme-catalyzed reactions have also been investigated. The various experiments are summarized in Table 6 and the relevant structures are shown on the next page. 

Figure 4. Enzyme mimic for chymotrypsin. (A) Structure and molecular weights. (Continued on next page.)...

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