Future protease activity

These must be worthwhile objectives and the recent identification by a number of research groups (see Skovronsky and Lee 2000 for description and details) of P-secretase as the membrane-bound aspartyl protease (RACE), S-site APP cleaving enzyme, paves the way for developing possible chemical inhibitors of its activity for experimental and clinical evaluation, although that remains for the future. 

The i-poly(3HB) depolymerase of R. rubrum is the only i-poly(3HB) depolymerase that has been purified [174]. The enzyme consists of one polypeptide of 30-32 kDa and has a pH and temperature optimum of pH 9 and 55 °C, respectively. A specific activity of 4 mmol released 3-hydroxybutyrate/min x mg protein was determined (at 45 °C). The purified enzyme was inactive with denatured poly(3HB) and had no lipase-, protease-, or esterase activity with p-nitro-phenyl fatty acid esters (2-8 carbon atoms). Native poly(3HO) granules were not hydrolyzed by i-poly(3HB) depolymerase, indicating a high substrate specificity similar to extracellular poly(3HB) depolymerases. Recently, the DNA sequence of the i-poly(3HB) depolymerase of R. eutropha was published (AB07612). Surprisingly, the DNA-deduced amino acid sequence (47.3 kDa) did not contain a lipase box fingerprint. A more detailed investigation of the structure and function of bacterial i-poly(HA) depolymerases will be necessary in future. 

Seen from the perspective of recent events, the clinical development of protease inhibitors follows rather conventional programs for drug development. The most remarkable characteristic of the clinical development of HIV-1 protease inhibitors is their rapid clinical evaluation, regulatory approval, and subsequent incorporation into standard treatment regimens. Undoubtedly, the pressure to develop new and active compounds to treat persons with HTV infection contributed to the urgency of drug development. This section will review the clinical milestones for HIV-1 protease inhibitors and discuss some of the near future clinical directions for these compounds. Peer-reviewed, published manuscripts are the basis for this review. Data presented at meetings and published in abstracts were not used. 

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