Protease acid

Osteoclasts are multinucleated cells derived from pluripotent hematopoietic stem cells. Osteoclasts possess an apical membrane domain, exhibiting a ruffled border that plays a key role in bone resorption (Figure 48-12). A proton-translocating ATPase expels protons across the ruffled border into the resorption area, which is the microenvironment of low pH shown in the figure. This lowers the local pH to 4.0 or less, thus increasing the solubility of hydroxyapatite and allowing demineralization to occur. Lysosomal acid proteases are released that digest the now accessible matrix proteins. 

The carboxyl proteases are so called because they have two catalytically essential aspartate residues. They were formerly called acid proteases because most of them are active at low pH. The best-known member of the family is pepsin, which has the distinction of being the first enzyme to be named (in 1825, by T. Schwann). Other members are chymosin (rennin) cathepsin D Rhizopus-pepsin (from Rhizopus chinensis) penicillinopepsin (from Penicillium janthinel-lum) the enzyme from Endothia parasitica and renin, which is involved in the regulation of blood pressure. These constitute a homologous family, and all have an Mr of about 35 000. The aspartyl proteases have been thrown into prominence by the discovery of a retroviral subfamily, including one from HIV that is the target of therapy for AIDS. These are homodimers of subunits of about 100 residues.156,157 All the aspartyl proteases contain the two essential aspartyl residues. Their reaction mechanism is the most obscure of all the proteases, and there are no simple chemical models for guidance. 

Pepsin consists of a single polypeptide chain of molecular weight 34 644 and 327 amino acid residues. Ser-68 is phosphorylated, but this phosphate may be removed without significantly altering the catalytic properties of the enzyme. As in other acid proteases, the active site is an extended area that can accommodate... 

About 80% of the fS-amviase present in wheat flour is associated with glutenins. Although acid proteases and peptidases are present in the wheat seed they do not normally cause problems in the bakery. 

The neuronal ceroid lipofuscinoses (CLN), also referred to as Batten s disease, are a group of disorders characterized by the accumulation of autofluorescent lipopigments. Clinical hallmarks include blindness, seizures, cognitive and motor decline and early death. Age of onset varies from infancy to adulthood. Eight genetic forms have been identified [4]. Two involve lysosomal acid hydrolases. CLN1 codes for palmitoyl protein thioesterase 1. Clinically it presents most often in infancy and leads to loss of active movement and visual contact by 3 years of age. It is most common in Finland, where its incidence is 1 20,000. CLN2 codes for a lysosomal pepstatin-insensitive acid protease. 

C. Multiple, partial, and other /3 barrels Acid proteases domains 1 and 2 Alcohol dehydrogenase domain 1 Pancreatic ribonuclease... 

Acid proteases, see Rhizopuspepsin Actinidin (Baker, 1980), see Papain Adenylate kinase (Schulz et ah, 1974a)... 

Barrels seem to prefer pure parallel or antiparallel /3 structure even more strongly than does /3 sheet in general. All the known singly wound barrels are pure parallel. An antiparallel barrel with an odd number of strands is constrained to have one parallel interaction, but no other parallel strand pairs occurs within antiparallel barrels except in the acid proteases. Also, even-stranded barrels are much more common than odd-stranded ones. 

Trypsin, chymotrypsin, elastase, etc. Subtilisin Papain, actinidin Thermolysin Carboxypeptidase Acid proteases Isomerases... 

Aspartic Proteinases. This group of proteinases is named for the aspartic acid residue in the active site. Previously, this group of enzymes was often referred to as the "acid proteases" (4). Members of this group are generally found only in eukaryotic organisms. However, clear evidence has been presented that certain viruses, most importantly the virus (HIV-1) considered to give rise to autoimmune deficiency disease (AIDS), and the polio virus, contain coding sequences for a dimeric aspartic proteinase which is involved in the... 

BPN is a 275 amino acid protease with a serine in the active site. Since it is functional in an alkaline environment it has potential use in detergent applications. Our program was to change specific characteristics of BPN to make it more effective in certain applications. Two main activities were targeted pH range and oxidative stability (since bleaches are often components of detergents). 

Signals of apoptosis lead to the activation of a family of intracellular cysteinyl aspartic acid proteases (caspases see Section 3.3) to play a pivotal role in the initiation and execution of apoptosis induced by various stimuli. Fourteen caspases in mammalian cell have been identified (W13). 

Fig. 1.10. Statine pharmacophore library targeting aspartic acid proteases (reprinted ( adapted or in part ) with permission from Journal of the American Chemical Society. Copyright 2001 American Chemical Society).

Powers JC, Harley AD, Myers DV. Subsite specificity of porcine pepsin. In Tang J, ed. Acid Proteases-Structure, Function and Biology. New York Plenum Press, 1977 141-157. 

Kirchgessner and Steinhart (52) studied the in vitro digestion of soy protein isolate with pepsin. They showed that a relatively higher percentage of the essential amino acids threonine, valine, isoleucine, leucine and phenylalanine were found in the undigested residue and therefore would be present in lower proportions in the hydrolysate. Myers et al. ( ) hydrolyzed a soy protein isolate with a fungal acid protease. They also found that the essential amino acid content of the hydrolyzate was lower than the isolate, but, as prepared by their continuous process, the hydrolyzate PER was not significantly reduced as compared to the isolate PER. 

Zevaco, C., Hermeir, J. and Gripon, J. C. 1973. Proteolytic system of Penicillium roque-forti. II. Purification and properties of the acid protease. Biochemie 55, 1353-1360. 

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