Hormones as enzyme inhibitors

Note Zollner (1993) in the main does not include hormones as enzyme inhibitors. Items that may be of particular interest are in boldface. 

Complementary structures of biological materials, especially those of proteins, often result in specific recognitions and various types of biological affinity. These include many pairs of substances, such as enzyme-inhibitor, enzyme-substrate (analog), enzyme-coenzyme, hormone-receptor, and antigen-antibody, as summarized in Table 11.2. Thus, bioaffinity represents a useful approach to separating specific biological materials. 

Hormones as well as vitamins also serve as enzyme inhibitors, as also presented in Table 3.3, which lists the enzymes inhibited corresponding to the tabulation provided in the Voet and Voet reference (Voet and Voet, 1995, p. 1263). 

Azapeptides are a unique class of pseudopeptides in which a nitrogen atom is substituted for the C H (Fig. 6) [136]. These analogues have been extensively used as enzyme inhibitors (ACE [137], serine protease [138] and hormone analogues [luteinizing hormone-releasing hormone (LHRH) [139], oxytocin, enkephalin] [136]. In the past few years, several groups have in-... 

In a very broad overview of the structural categories one can state several statistical correlations with type of function. Hemes are almost always bound by helices, but never in parallel a//3 structures. Relatively complex enzymatic functions, especially those involving allosteric control, are occasionally antiparallel /3 but most often parallel a//3. Binding and receptor proteins are most often antiparallel /3, while the proteins that bind in those receptor sites (i.e., hormones, toxins, and enzyme inhibitors) are most apt to be small disulfide-rich structures. However, there are exceptions to all of the above generalizations (such as cytochrome cs as a nonhelical heme protein or citrate synthase as a helical enzyme), and when one focuses on the really significant level of detail within the active site then the correlation with overall tertiary structure disappears altogether. For almost all of the dozen identifiable groups of functionally similar proteins that are represented by at least two known protein structures, there are at least... 

There are many natural and biological macromolecules that possess anticancer activity. Cytokines, topoisomerase inhibitors, monoclonal antibodies, thymic hormones, cell growth inhibitors, and enzymes have been used [68], They have been recently reviewed [59,69] and their detailed description is beyond the scope of this article. The main problems connected with the administration of such natural macromolecules is their short intravascular half-life, immunogenicity, and sometimes poor solubility. Their modification with synthetic macromolecules can dramatically increase their therapeutic potential as described below. 

Enzyme inhibitors can reduce the metabolic barrier to nasal delivery. The selection of an inhibitor is made on the basis of its ability to inhibit effectively the enzyme primarily responsible for the degradation of a particular compound. The coadministration of peptidase and protease inhibitors such as bacitracin, bestatin, amastatin, and aminoboronic acid derivatives has been found to promote the absorption of LHRH and growth hormone [42,43]. Aminopeptidase inhibitors in particular are effective in improving the bioavailability of enkephalins [44]. 

The concept of photoswitchable biomaterial can be extended to different biological functions, such as cofactors, inhibitors, enzymes, receptors, hormones, antigens/antibodies, DNA, etc. This opens a broad spectrum of applications in different biomaterial science disciplines. 

Aminocyclopropanecarboxylic acid (74) has attracted special interest (a) as a modified model of natural a-amino acids, in the synthesis of bioactive peptide analogs, potential enzyme inhibitors , or e.g. a derivative with sweetness receptor activity s and (b) together with its Schiff-base metal complexesas the biosynthetic precursor of ethene, the plant ripening hormone . (See these sources and the review in Reference 135 for further references.)... 

Phosphate buffer, azide free, 0.1-0.5 M, is suitable for the iodination reaction, but the enzymes and hormone should be diluted in 10—50 mM buffer, as the higher molarity may cause aggregation. There must be no azide or other enzyme inhibitors in the buffers used for the iodination reagents. 

---