Disease relevance of CYM

• The crystal structure of recombinant bovine chymosin (EC 3.4.23.4; renin), which was cloned and expressed in Escherichia coli, has been determined using X-ray data extending to 2.3 A resolution [1].
• A full-length cDNA copy of the mRNA encoding calf chymosin (also known as rennin), a proteolytic enzyme with commercial importance in the manufacture of cheese, has been cloned in an f1 bacteriophage vector [2].
• In contrast, the activities of pepsin A and chymosin required to affect Helicobacter motility were ten times higher [3].
• When anti-sera to bovine pepsinogen and chymosin (rennin) was used, immunoreactive tumor cells were found in 12 of 23 gastric adenocarcinomas irrespective of the tumor subtype, degree of differentiation, or the presence or absence of intestinal metaplasia in the adjacent gastric mucosa [4].
• AIMS: The present study was designed to determine the individual and combined effects of acidified sodium chlorite (ASC, 0.1%, 24 +/- 1 degrees C), cetylpyridinium chloride (CPC, 0.5%, 24 +/- 1 degrees C) and hot water (HW, 93 +/- 1 degrees C) treatments on the survival of Listeria monocytogenes and Staphylococcus aureus [5].

High impact information on CYM

• The enzyme has been purified from bacteria by extraction with urea and chromatography on DEAE-cellulose and converted to enzymatically active chymosin by acidification and neutralization [6].
• The complete amino acid sequence of calf chymosin (rennin) (EC 3.4.23.4) has been determined [7].
• Other acid proteases, human pepsin, human gastricsin, renin, cathepsin D, the acid protease from Rhizopus chinensis and bovine chymosin, also are inhibited by pepstatin and its derivatives [8].
• The nucleotide sequence is in substantial agreement with the reported amino acid sequence of prochymosin and shows that this protein has a mol.wt. of 40431 and chymosin a mol.wt. of 35612 [9].
• The structure of calf chymosin (EC 3.4.23.3), the aspartic proteinase from the gastric mucosa, was solved using the technique of molecular replacement [10].

Biological context of CYM

• Although chymosin has a broad specificity, it has been possible to selectively study the hydrolysis of two bonds (Ala-189-Phe-190 and Leu-192-Tyr-193) by choosing appropriate conditions [11].
• Peptide substrates for chymosin (rennin). Interaction sites in kappa-casein-related sequences located outside the (103-108)-hexapeptide region that fits into the enzyme's active-site cleft [12].
• Kinetics of action of chymosin (rennin) on some peptide bonds of bovine beta-casein [11].
• Role of S'1 loop residues in the substrate specificities of pepsin A and chymosin [13].
• The diagrams derived from this treatment allowed us to study the chymosin sensitive bond (milk-clotting process), as well as the glycosylation and phosphorylation sites, found to be situated in beta-turns [14].

Anatomical context of CYM

• In vitro translation of total poly(A)-enriched RNA from the calf fourth stomach (abomasum) and immunoprecipitation with antichymosin antiserum revealed that a form of chymosin (probably preprochymosin judging from the Mr-value) is the major in vitro translation product of RNA from that tissue [2].
• RESULTS: Refolding of 1.0 mg/ml of protein inclusion bodies diluted in phosphate buffer at 0.32 M urea in the presence of alpha-crystallin resulted in enhanced chymosin activity relative to the control without alpha-crystallin [15].
• The staining properties and chymosin sensitivity of this fraction were compared with those of human milk and bovine casein proteins [16].
• By extending the chromatofocusing technique to a very acidic pH range (down to pH 2.0) a method which, in a single-step procedure, allows separation of the three main aspartic proteases secreted by the bovine abomasal mucosa i.e., chymosin (EC 3.4.23.4), gastricsin (EC 3.4.23.3), and pepsin A (EC 3.4.23.1), has been developed [17].
• Postoperatively they received either pig chow (n = 14), nonpolymeric (elemental) infant formula (n = 7), or polymeric infant formula alone (n = 8) or supplemented either with fiber (n = 6) or with bovine colostrum protein concentrate (CPC; n = 10) for 8 weeks until sacrifice [18].

Associations of CYM with chemical compounds

• The sharp lines in the casein micelle spectrum are further sharpened by addition of chymosin and broadened markedly by addition of ethanol [19].
• Calf chymosin was shown to catalyse peptide synthesis optimally over the range pH 4-5, giving satisfactory yields of methyl esters or p-nitroanilides of benzyloxycarbonyl tetra- to hexa-peptides, provided that hydrophobic amino-acid residues form the new peptide bonds [20].
• A carbohydrate-free fraction as well as two NeuAc-containing fractions were compared in their substrate behaviour towards the action of the milk-clotting enzyme chymosin at pH 6.6 and 30 degrees C. To this end the trichloroacetic acid-soluble reaction products were analysed by high-performance gel-permeation chromatography [21].
• The action of chymosin on the Phe23-Phe24 bond of bovine alpha s1-casein, in citrate buffer (pH 6.2) at 30 degrees C, was followed by reversed-phase HPLC quantification of residual alpha s1-casein or fragment 24-199 after different time periods and at different substrate concentrations [22].
• Identification of human milk kappa-casein on polyacrylamide gels by differential staining with Ethyl-Stains-all and chymosin sensitivity [16].

Other interactions of CYM

• Several peptides sharing high sequence homology with lactoferricin B (Lf-cin B) were generated from bovine lactoferrin (Lf) with recombinant chymosin [23].
• The molecular events occurring during the primary phase of chymosin action on k-casein are discussed [24].
• The gene encoding chymosin has been cloned and expressed in suitable bacteria and yeast hosts under the control of lac, trp, trp-beta, gly A genes, and serine hydroxymethyl-transferase promoters [25].

Analytical, diagnostic and therapeutic context of CYM

• Molecular cloning and characterization of double-stranded cDNA coding for bovine chymosin [2].
• Because the residues in the loop appeared to be involved in the unique specificities of respective types of enzymes, site-directed mutagenesis was undertaken to replace pepsin-A-specific residues by chymosin-specific ones and vice versa [13].
• Characterization of bovine kappa-casein fractions and the kinetics of chymosin-induced macropeptide release from carbohydrate-free and carbohydrate-containing fractions determined by high-performance gel-permeation chromatography [21].
• The first steps of proteolysis of bovine beta-casein by chymosin were studied quantitatively by using reverse-phase high-performance liquid chromatography (RP-HPLC) [11].
• Circular dichroism spectra of a series of synthetic, kappa-casein-related oligopeptide substrates for chymosin in water and in surfactant solution were determined [26].

References