A-Lytic proteases

Support for this concept is provided by H NMR studies which have identified a downfield resonance of the hydrogen-bonded proton in this pair at 18 ppm in chymotrypsinogen and chymotrypsin at low pH and at 14.9-15.5 ppm at high pH values.246 247 Similar resonances are seen in the a-lytic protease,248 in sub-tilisin,249 in adducts of serine proteases with boronic acids250 251 or peptidyl trifluoromethyl ketones,252 in alkylated derivative of the active site histidine,253 and in molecular complexes that mimic the Asp-His pair in the active sites of serine proteases.254... 

Finally, serine protease from parasites and pathogens can mimic the biological roles of proteases in normal cells. Release of protease from parasites and pathogens can activate cells and produce an inflammatory response. Many pathogens and parasites contain cathepsins and elastases along with many of other serine or serine-like proteases like Streptomyces griseus A or B and a-lytic protease that lead to the invasion of abnormal cells and tissue... 

The charge relay system is found at the active site of a group of enzymes called serine proteases. They include chymotrypsin, trypsin, a-lytic protease, elastase, and subtilisin. It is interesting that the charge relay system was found in enzymes belonging to different branches of diemical evolution (chymotrypsin and subtilisin). This suggests that this system is a hydrolytic catalytic system of general importance which is derived solely from amino acid residues. 

Chymotrypsin / Trypsin I a-Lytic protease Elastase Subtilisin -OH (Ser), (His), -COOH (Asp) HN- ... 

Chapman and Liljas, Fig. 4. The serine protease fold. The serine proteases have two domains with the same topology. The six strands in the j3 barrel are denoted 1-6. The active site is in the cleft between these domains, (a) a-Lytic protease (Fujinaga et al, 1985) (b) the fold of the Sindbis coat protein (Choi et al., 1996). The corresponding strands in the two proteins are colored in the same way to simplify the comparison. 

Sequence 1, in Table I, is the sequence of trypsin, chymotrypsin, pancreatic elastase, thrombin, and other mammalian proteases, and it occurs throughout the animal kingdom down to invertebrates as primitive as the sea anemone (4). The Streptomyces griseus enzymes are from Pronase, a commercial enzyme preparation. Two of its components, Streptomyces griseus trypsin and protease A, not only have the Asp.Ser.Gly sequence, but they show several other homologies in sequence with the mammalian enzymes (5, 6), The same is true for the sequence of a-lytic protease, the Myxobacter 495 enzyme (7). 

Hunkapiller et al. (31, 32) approached the problem in a radically different way. They determined the pH dependence of the parameters of the nuclear magnetic resonance spectrum for a bacterial protease which had been specifically enriched with at C-2 of its single histidine residue. The enzyme, a-lytic protease (33), is listed in Table I. The reasons for choosing it for this investigation are as follows. 

These measurements assign a pKn of <4 to the imidazole ionization of a-lytic protease. The low pK indicates that the conjugate base (neutral... 

Table III. Chemical Shift and Coupling Constant Values for C-2 Carbon in Histidine Residue of a-Lytic Protease...

Figure 5. Variation of the protein MEP along the active sites of some enzymes. It a-chymotiypsin, 2t p-tiypsin, 3 porcine pancreatic elastase, 4 Streptomyces Griseus hydrolase, Si a-lytic protease, 6t subtilisin NOVO, 7i acetylcholinesterase, 8> lipase A, 9 lysozyme, lOi D-xyloie isomerase. Point A is at OG of die active serine in 1-8, at the bisector ofODl and OD2 of Asp-52 in 9, at Ol of the cyclic xylose m 10. Point B is atNE2 of the catalytic histidine in 1-8, in the first trisector of points A and Din 9, atNEl ofHis-S4in 10. Point C is at ND1 of the catalytic histidine in 1-8 and 10, at the second trisector of points A and D in 9. Point D is at the bisector of the carboxylate oxygens of the catalytic Asp or Glu side chains.

Filtered culture broth was used as the enzyme source. Details of the enzyme production are given elsewhere (27,28). The lytic activity of the Oerskovia system is due to a lytic protease and an endo 6(1,3) glucanase (20), possibly supplemented with an exo 6(1-3) glucanase removing a 5-sugar unit from the chain (29). 

Hunkapiller, M. W., Smallcombe, S. H., and Richards, J. H. (1975). Org. Mag. Res. 7, 262. Mechanism of Serine Protease Action. Ionization Behaviour of Tetrahedral Adduct Between a-Lytic Protease and Tripeptide Aldehyde Studied by Carbon-13 Magnetic Resonance. 

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