Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Riboflavin-binding protein of hen egg white (egg-white RBP) comprised 219 amino acid residues and nine disulfide bonds. To identify the locations of these bonds, the native protein was oxidized with cyanogen bromide and digested with trypsin, thermolysin, and Staphylococcus aureus V8 protease. The cystine-containing peptides were isolated by HPLC. Amino acid analyses and amino acid sequence analyses of the reduced pyridylethylated derivatives of the cystine peptides showed that seven of the disulfide bonds were as follows: Cys(24)-Cys(73), Cys(57)-Cys(138), Cys(64)-Cys(110), Cys(99)-Cys(169), Cys(116)-Cys(134), Cys(103)-Cys(152), Cys(167)-Cys(202). The other two disulfide bonds were either Cys(5)-Cys(32) and Cys(33)-Cys(77) or Cys(5)-Cys(33) and Cys(32)-Cys(77).
 ...
PMID:Positions of disulfide bonds in riboflavin-binding protein of hen egg white. 357 Dec 3

Vitamin B2 and flavin cofactors are transported tightly bound to immunoglobulin in human serum. We reasoned that anti-mitochondrial flavoprotein autoantibodies (alpha Fp-AB) present in the serum of patients with myocarditis and cardiomyopathy of unknown aetiology may form immunoglobulin aggregates with these serum proteins. However, immunodiffusion and Western blot assays demonstrated that the flavin-carrying proteins were not recognized by alpha Fp-AB. Apparently the flavin moiety in the native protein conformation was inaccessible to alpha Fp-AB. This conclusion was supported by the absence of an immunoreaction between the riboflavin-binding protein from egg white and alpha FP-AB. Intravenous application of vitamin B2 to rabbits immunized with 6-hydroxy-D-nicotine oxidase, a bacterial protein carrying covalently attached FAD, did not neutralize alpha Fp-AB which had been raised in the serum of the animals. FAD-carrying peptides generated from 6-hydroxy-D-nicotine oxidase by trypsin and chymotrypsin treatment were not recognized by the alpha Fp-AB, but those generated by endopeptidase Lys were. This demonstrates that the epitope recognized by alpha Fp-AB comprises, besides the flavin moiety, protein secondary structure elements.
 ...
PMID:Anti-mitochondrial flavoprotein autoantibodies of patients with myocarditis and dilated cardiomyopathy (anti-M7): interaction with flavin-carrying proteins, effect of vitamin B2 and epitope mapping. 1019 10

Riboflavin (RF) upon irradiation with fluorescent light generates reactive oxygen species like superoxide anion, singlet and triplet oxygen, flavin radicals and substantial amounts of hydrogen peroxide (H2O2). H2O2 can freely penetrate cell membrane and react with a transition metal ion like Cu(ll), generating hydroxyl radical via the modified metal-catalyzed Haber-Weiss reaction. Earlier, it was reported that trypsin-chymotrypsin mixture served as an indirect antioxidant and decreased free radical generation. Thus, in the present study, we used photoilluminated RF as a source of ROS to investigate the effect of free radicals on the activity of trypsin. We also compared the damaging effect of photoilluminated RF and RF-Cu(ll) system using trypsin as a target molecule. RF caused fragmentation of trypsin and the effect was further enhanced, when Cu(II) was added to the reaction. Results obtained with various ROS scavengers suggested that superoxide radical, singlet and triplet oxygen were predominantly responsible for trypsin damage caused by photoilluminated RF. On the other hand, when Cu(ll) was added to the reaction, hydroxyl radical was mainly responsible for trypsin damage. A mechanism of generation of various ROS in the reaction is also proposed. Trypsin did not show any antioxidant effect with RF alone or with RF-Cu(II) combination.
 ...
PMID:Photoilluminated riboflavin/riboflavin-Cu(II) inactivates trypsin: Cu(II) tilts the balance. 1713 39

Riboflavin is the biological precursor of two important flavin cofactors-flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN)-that are critical prosthetic groups in several redox enzymes. While dietary supplementation with riboflavin is a recognized support therapy in several inborn errors of metabolism, it has yet unproven benefits in several other pathologies affecting flavoproteins. This is the case for glutaric aciduria type I (GA-I), a rare neurometabolic disorder associated with mutations in the GCDH gene, which encodes for glutaryl-coenzyme A (CoA) dehydrogenase (GCDH). Although there are a few reported clinical cases that have responded to riboflavin intake, there is still not enough molecular evidence supporting therapeutic recommendation. Hence, it is necessary to elucidate the molecular basis in favor of riboflavin supplementation in GA-I patients. Here, using a combination of biochemical and biophysical methodologies, we investigate the clinical variant GCDH-p.Val400Met as a model for a phenotype associated with severe deflavinylation. Through a systematic analysis, we establish that recombinant human GCDH-p.Val400Met is expressed in a nonfunctional apo form, which is mainly monomeric rather than tetrameric. However, we show that exogenous FAD is a driver for structural reorganization of the mutant enzyme with concomitant functional recovery, improved thermolability, and resistance to trypsin digestion. Overall, these results establish proof of principle for the beneficial effects of riboflavin supplementation in GA-I patients.
 ...
PMID:Functional Recovery of a GCDH Variant Associated to Severe Deflavinylation-Molecular Insights into Potential Beneficial Effects of Riboflavin Supplementation in Glutaric Aciduria-Type I Patients. 3299 90