Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We present in this paper the sequence of the heme-binding domain of chicken sulfite oxidase which can be obtained by chymotryptic digestion of the native enzyme. The results of an automatic degradation have been reported previously. In the present work peptides were obtained from the heme-binding domain by digestion with trypsin, chymotrypsin and Staphylococcus aureus V8 protease; they were manually sequenced by the dansyl/Edman procedure. The evidence thus obtained is sufficient to completely establish the order of the 97 residues. In addition, two rounds of Edman degradation on sulfite oxidase itself allowed us to identify the same two residues, H-Ala-Pro, present at the N-terminus of the heme-binding domain; this result suggests that the latter constitutes the amino-terminal end of the sulfite oxidase peptide chain. The data presented here confirm the strong similarity between sulfite oxidase and microsomal cytochrome b5 already suggested by our first results. A sequence alignment is proposed for the two proteins. Inspection of the calf liver cytochrome b5 three-dimensional model together with the alignment suggests a similar overall structure for sulfite oxidase core with a limited number of backbone modifications. Our results point to a common evolutionary origin for sulfite oxidase core and microsomal cytochrome b5.
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PMID:Amino acid sequence of the 'b5-like' heme-binding domain from chicken sulfite oxidase. 51 Feb 90

It is known that each subunit of the tetrameric flavocytochrome b2 can be cleaved by yeast proteases to fragments of molecular weight 33-36000 and 21 000, with some modification of catalytic properties, but without destruction of the oligomeric state of the protein. We report here experimental conditions which enabled us to simulate this specific cleavage in a controlled fashion with chymotrypsin and subtilisin. With trypsin and papain, on the other hand, it was not found possible to stop the digestion in such a way as to obtain a homogeneous still active product. A characterization of the enzymatic forms obtained by digestion with chymotrypsin and subtilisin at 0 degrees C shows that modification of enzymatic and solubility properties occurs in a stepwise fashion. It is also ccluded that cleavage by yeast proteases is accompanied by loss of 10 to 25 residues. At 37 degrees C, chymotrypsin digestion yields a heme-binding core of molecular weight 15 000, larger than the already characterized tryptic heme-binding core by about 40 residues. Although the latter is known to be very similar to trypsin-solubilized cytochrome b5, the lack of aggregation of the former in aqueous solution, its amino acid composition and circular dichroism spectra do not point to a similarity of its additional peptide segment with the hydrophobic tail of detergent-solubilized cytochrome b5.
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PMID:Controlled proteolysis of flavocytochrome b2. Characterization of a 15000-dalton heme-binding core and comparison with detergent solubilized cytochrome b5. 78 77

The myoglobin, cytochrome b5 and alpha-chymotrypsin hydrophobic nucleus sizes were calculated as well as sizes of theoretical spherical nucleus, radii that are equal to the lengths of phenylalanine and tryptophan lateral groups. All calculated values of sizes lie in the (0.99-1.65) nm3 interval. The quantitative estimation of analyzed proteins nucleus heterogeneous composition has been shown.
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PMID:[A comparative analysis of the structure of the myoglobin, cytochrome b5, and alpha-chymotrypsin hydrophobic nuclei]. 181 2

The complete primary structure of bovine heart cytochrome c1 was established by analyses of peptide fragments prepared by digestion using trypsin, staphylococcal protease, and chymotrypsin and by cyanogen bromide cleavage of cytochrome c1 and its derivatives. The total number of amino acid residues is 241, giving a molecular weight of 27,924 including the heme group. The NH2- and COOH-terminal residues are serine and lysine, respectively. One characteristic of the protein is that cytochrome c1 contains 43.6% hydrophobic residues and the polarity is estimated to be 41.1%. No clear homology was found between cytochrome c1 and other membranous proteins such as cytochrome b5 or the subunits of cytochrome oxidase for which sequences have been reported. Cytochrome c1 is predicted to have a high content of alpha-helix (46%). Partial sequence studies were also carried out on cytochrome c1 preparations obtained by different procedures and showed that there is no difference among the sequences of various preparations of cytochrome c1. The presence of a hydrophobic cluster near the COOH-terminal region indicates that the COOH-terminal region of cytochrome C1 associates with, or is buried in, the phospholipid bilayer of the mitochondrial membrane.
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PMID:Structural studies of bovine heart cytochrome c1. 628 15

NADH-cytochrome b5 reductases purified from human red cell membranes and cytosol were compared with those prepared from human liver microsomes. Minimal molecular weights of the membrane and the cytosol enzymes as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were 36,000 and 32,000 daltons, respectively, which are comparable to those of the detergent-solubilized reductase (dfp) and the protease-solubilized one (tfp) of liver microsomes, respectively. All the enzymes contained FAD and had essentially the same turnover numbers and apparent Km values for NADH and protease-solubilized cytochrome b5. The membrane enzyme and liver dfp reduced cytochrome c in the presence of detergent-solubilized cytochrome b5 70-80 times faster than in the presence of trypsin-solubilized cytochrome b5, whereas the cytosol enzyme and liver tfp showed essentially the same low activities with both preparations of cytochrome b5. SDS-PAGE mapping of the limited proteolytic products of the reductases obtained by digestion with staphylococcal protease or a-chymotrypsin showed essentially the same patterns of peptides between the red cell membrane enzyme and liver dfp and between the red cell cytosol enzyme and liver tfp. These results suggest that the NADH-cytochrome b5 reductase of human red cell membranes is identical with that of liver microsomes and that the enzyme of red cell cytosol is a proteolytic product of the membrane enzyme.
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PMID:Human NADH-cytochrome b5 reductases: comparison among those of erythrocyte membrane, erythrocyte cytosol, and liver microsomes. 684 58

Flavocytochrome b2 from baker's yeast is a bifunctional tetrameric protein which carries two prosthetic groups, FMN and heme, per subunit of Mr 58 000. The amino terminus of the subunit is wrapped around the heme and constitutes the so-called cytochrome b2 core (Mr 11 000), homologous to cytochrome b5. It has been shown in the past that a number of proteases (yeast proteases, chymotrypsin) preferentially cleave the peptide chain at a point situated much further down the polypeptide chain than the C terminus of the heme-binding domain. Some enzymatic parameters are concomitantly modified, but not the quaternary structure. This paper describes the conditions for selective proteolysis of intact flavocytochrome b2 and of its various previously studied stable nicked forms by the protease from Staphylococcus aureus V8. Successive attack by a combination of two proteases is also described. We have established the amino acid sequence of the area where proteolytic attack takes places, and shown that chymotrypsin and S. aureus protease open only one bond, whereas yeast proteases remove five residues from the central part. The various nicked forms, some of which have lost up to 16 amino acid residues, have been enzymatically characterized. These and previous results lend support to, but do not prove, the idea that the flavodehydrogenase part of flavocytochrome b2 may be composed of two domains, linked by the region accessible to proteases. That area might constitute a hinge or rather a clasp between the domains.
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PMID:Study of a zone highly sensitive to proteases in flavocytochrome b2 from Saccharomyces cerevisiae. 703 12

Haem containing fragments of cytochrome b5 prepared from rabbit liver microsomes by trypsin and chymotrypsin treatment, and checked by isoelectrofocussing, were identified as sequences 1--90 (tryptic fragment) and 12--97 (chymotryptic fragment) of the protein. The two fragments exhibit the same helix content as judged from circular dichroism spectra. Thermal unfolding measured by scanning microcalorimetry proceeds as a two-state process at transition temperatures Ttrs equals 70 degrees C (fragment 1--90) and Ttrs equals 73 degrees C (fragment 12--97) at neutral pH. The Gibbs energy change at unfolding of the fragments calculated from the calorimetric results amounts to delta G25 degrees equals 26 + or minus 2 kJ mol-1. The results indicate that the region ranging at least from residues 90--97 does not essntially contribute to the secondary structure and stability of the haem containing domain of cytochrome b5. The findings confirm the existence of a junction region between the membrane binding moiety and the haem containing domain of cytochrome b5 which enables lateral movement of the functionally important part of the molecule to certain extent.
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PMID:Optical and thermodynamical properties of proteolytic fragments of cytochrome b5. 742 36

It has been found that hydrophobic potentials of 30- to 40-amino acid fragments of amino acid sequences of myoglobin, cytochrome b5, alpha-chymotrypsin, and seven other globular proteins analyzed are similar and correspond to free energies of formation of limited hydrophobic nuclei.
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PMID:Role of hydrophobic interactions in protein chain folding during biosynthesis. 963 93