Endogenous proteases

In some instances it may be necessary to demonstrate that all traces of specific contaminants have been removed prior to final product filling. This would be true, for example, of many proteolytic inhibitors added during the initial stages of downstream processing to prevent proteolysis by endogenous proteases. Some such inhibitors may be inherently toxic, and many could (inappropriately) inhibit endogenous proteases of the recipient patient. 

Dieldrin accumulated in proportion to incubation time during the first 30 min and declined thereafter, like the biphasic curves for aldrin epoxidation in other insects (11, 26). The rate curve declined continuously to 50% of maximum after 60 min of incubation at 30°C. BSA did not increase epoxidase activity in 15 min incubations (Table V) or 60 min incubations (Table IV). Consequently, reduced epoxidase activity is probably not due to endogenous proteases in the homogenate (1). 

Weakly active mutants were successfully expressed by co-culturing the mutants with a small amount of a helper of B. subtilis containing wild-type protease.34 The small amounts of highly active wild-type protease, plus any other endogenous proteases, will mask residual activity in debilitated mutants. This problem was overcome by introducing a surface mutation, Ser —> Cys-24. The thiol group of the Cys binds reversibly to an activated thiol sepharose column, and so mutants may be selectively fished out from contaminants.34... 

Suzuki Y, Koyama J, Moro O, et al. The role of two endogenous proteases of the stratum corneum in degradation of desmoglein-1 and their reduced activity in the skin of ichthyotic patients. Br J Dermatol 1996 134 460-464. 

Degradation in the gut is caused by endogenous proteases such as trypsin and a-chymotrypsin. Entrapment of maoramolecules in liposomes results in better nrntectian asainst nrntealvsis T301. Since lin id-soluble molecules m absorbed... 

A better understanding of the structure of collagen IV molecules explains some previous observations. The occurrence of the 7 S domain and nonhelical interruptions in the molecule can explain in part the heterogeneous mixture of collagenous components isolated from basement membrane, particularly when pepsin or other proteases are used to solubilize the protein. The molecules isolated from lathyritic basement membrane by acid extraction are truncated and lack the 7 S domain presumably due to cleavage by endogenous proteases. 

There is evidence that protein structures are also responsible for cell cohesion in nonpalmo-plantar stratum corneum. When punch biopsies of normal human gluteal skin were incubated in a buffer containing a mixture of the zwitterionic surfactant /V,/V,-dimethyldodecylamine and the anionic surfactant sodium dodecyl sulfate,11 there was dissociation of cells in the stratum corneum but not in the rest of the epidermis. The cell dissociation took place only in the presence of EDTA and was inhibited by the serine protease inhibitor aprotinin.12 Suzuki et al.13,14 presented evidence that spontaneous cell dissociation in nonpalmo-plantar stratum corneum could be inhibited by a combination of inhibitors of trypsin-like and chymotrypsin-like enzymes. Thus, nonpalmo-plantar stratum corneum contains endogenous proteases that mediate cell dissociation. 

Suzuki, Y., Nomura, J., Koyama, J., Takahashi, M., and Horii, I., Detection and characterization of endogenous protease associated with desquamation of stratum corneum, Arch. Dermatol. Res., 285, 372, 1993. 

Proteases are regulated in vivo by autoinhibition (as zymogens), proteolytic activation, turnover and by endogenous protease inhibitor proteins. The following brief sketch of protease complexity is accompanied by succinct reference to the physiological context and hence the potential pharmacological relevance of plant-derived protease inhibitors to be described later in this review. 

Animal proteases, particularly those involved in blood clotting, can be also regulated by endogenous protease inhibitory proteins that act as inhibitory substrate analogues. These inhibitor proteins bind at the active site through key inhibitory sequences in which the key residues about the peptide bond contribute to inhibition and are denoted (N-terminal side)—P2—PI—(peptide bond to be hydrolysed)-PT-P2 -(C-terminal side) or simply P2-P1-PT-P2. A large number of plant PI proteins also act as peptide substrate mimetics. 

Table VI. The Effect of Succinylation on Proteolysis of Yeast Proteins by Endogenous Proteases During Incubation (pH 6.0, 55°C) for RNA Reduction...

The sensory quality of meat and seafood is significantly affected by endogenous proteases. The lysosomes contain, among other enzymes, at least 12 cathepsins,... 

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