Elastase characteristic

A different strategy for measuring protease activity is based on the property of xanthene dyes to form H-type dimers (see Sect. 6.2.3) when they are in close proximity. These dimers are accompanied with a characteristic quenching of their fluorescence and, particularly for rhodamines, with a blue shift in the absorption spectrum [121, 122]. The probe D-NorFES-D designed to measure activity of elastase in HL-60 cells consists of an undecapeptide derivatized with one tetramethylrhodamine dye on each side. The sequence contains proline residues to create a bent structure and bring the two fluoro-phores in close proximity. Intact D-NorFES-D shows 90% of its fluorescence quenched plus a blue shift of the absorption spectrum. After addition of the serine protease elastase, an increase in the fluorescence and a bathochromic shift of the absorption spectrum is observed, resulting in an increase in the emission ratio [80],... 

Theoretically, all of the proteinaceous inhibitors act by presenting a loop portion of their chains as an idealized, that is, pre-organized for optimal interactions, substrate for elastase. Conformational analysis of the inhibitor residues P P3 and P1-P3 for a series of proteinaceous, serine protease inhibitors showed that there is little difference between their free and/or complexed states [63]. In aj-PI, the loop contains as its elastase reactive center (see Table 2.2) a Met-Ser linkage. The importance of the P,-substituent in a PI for its enzyme specificity characteristics is exempli-... 

Most enzymes present in the body play an essential biochemical role, but several of them also have an undesirable characteristic which requires selective suppression. Thus, the degrading effect of human leukocyte elastase on elastin (which provides elastic properties in several organs) requires selective inhibitors which are discussed in Chapter 2. 

All the isozymes have a lot of overlapping identical residues and some regions of the sequences show similar characteristics to serine-like proteases, such as elastase and coagulation factor IX. The N-terminal sequences of F-III-1 and -III-2 are identical, and so are those of F-I-l and F-I-2, respectively. So far, several complete reading frames (amino acid sequences) of the isozymes, F-III-1 and -III-2 (L. rubellus) [24,28], EFE... 

In the recent studies, the enzyme shows that the overall polypeptide fold of chymotrypsin-like serine protease possesses essential SI specificity determinants characteristic of elastase using the multiple isomorphous replacement (MIR) method and refined to 2.3 A resolution Fig. (5). Structure-based inhibitor modeling demonstrated that EFEa s SI specificity pocket is preferable for elastase-specific small hydrophobic PI residues, while its accommodation of long and/or bulky PI residues is also feasible if enhanced binding of the substrate and induced fit of the SI pocket are achieved [Fig. (6) shows the active sites of serine protease]. EFEa is thereby endowed with relatively broad substrate specificity, including the dual fibrinolysis. This structure is the first report of an earthworm fibrinolytic enzyme component, a serine protease originated from annelid worm [17]. 

---