Disease relevance of Cyb5

• Turnover of cytochrome P-450 and cytochrome b5 hemes in griseofulvin-induced murine porphyria [1].
• However, injection of these mice with 0.5 mg/kg body weight of E.coli endotoxin (Westphal extracted) produced a decrease in the rate of N-demethylation of ethylmorphine and in the levels of cytochrome P-450 and cytochrome b5 comparable to that observed in the endotoxin-sensitive C3H/HeJ mouse strain [2].
• This protective effect of BNF on O2 toxicity in C57BL/6J mice was associated mainly with a large increase in the components of the cytochrome P-450 system (cytochrome P-450 and cytochrome b5) in the lung [3].
• Involvement of cytochrome b5 in the cytotoxic response to Escherichia coli lipopolysaccharide [4].

High impact information on Cyb5

• By difference spectrophotometry, the pellet was shown to contain cytochrome b5 and cytochrome P-450, hemeproteins that have been shown to participate in electron-transport reactions of endoplasmic reticulum and other membranous fractions of various tissues [5].
• These findings are supportive of our hypothesis that soluble cytochrome b5 of erythrocytes is derived from endoplasmic reticulum or some other membrane structure of immature erythroid cells during cell maturation [5].
• We failed to detect soluble cytochrome b5 in the 105,000-g supernatant fraction from homogenates of untreated or dimethyl sulfoxide-treated T-3-Cl-2 cells [5].
• A reconstitution experiment with the purified CMP-NeuAc hydroxylase, soluble cytochrome b5, and recombinant NADH-cytochrome b5 reductase revealed that these three factors are essential for the reaction [6].
• Stearoyl-CoA desaturase, cytochrome b5 and carboxylesterase are endoplasmic reticulum membrane-bound enzymes involved in fatty acid metabolism [7].

Chemical compound and disease context of Cyb5

• Camphor only at the 300 mg/kg body weight dose level caused a significant increase in the activities of cytochrome P450 (P < 0.05), cytochrome b5 (P < 0.05), aryl hydrocarbon hydroxylase (P < 0.05) and glutathione S-transferase (P < 0.05) [8].
• In comparison to control mice, toxaphene-treated mice had increased liver weight, increased liver/body weight ratios and increased levels of total hepatic CYP and cytochrome b5 [9].

Biological context of Cyb5

• Coumarin 7-hydroxylation activity is greatly stimulated by cytochrome b5 only when Phe is at position 209, while cytochrome b5 stimulates testosterone hydroxylation activity of P450coh in which Phe, Asn, Ser or Lys substitutes residue 209 [10].
• In contrast, extramitochondrial cytochrome c does not stimulate respiration in permeabilized control cells, and catalyzes only a low rate of oxygen consumption via electron transfer to cytochrome b5 on the outer mitochondrial membrane [11].
• Based on its partial amino acid sequence and immunological cross-reactivity, this protein was identified as soluble cytochrome b5 lacking the membrane domain of microsomal cytochrome b5 [12].
• The LD50 dose of all three toxicants after 0.75 h of administration could increase cytochrome P-450 and cytochrome b5 contents (82-143%), and the 1/4 LD50 of these compounds could elicit the same effect after 168 h (168-393%) [13].
• The modulatory effects on biochemical parameters including glutathione S-transferase (GST), cytochrome b5, cytochrome P-450, acid soluble sulfhydryl (-SH) content and microsomal lipid peroxidation (MDA) levels were assessed [14].

Anatomical context of Cyb5

• The activity of dihydroceramide:sphinganine C-4-hydroxylase was reconstituted with the purified FLAG-Des2, mb5 (the membrane form of cytochrome b5) and bovine erythrocyte membrane [15].
• Addition of BHA to the diet significantly lowered the content of cytochrome P-450 in liver nuclei and increased the specific activity of NADPH-cytochrome c reductase and the content of cytochrome b5 in liver microsomes [16].
• An unusual effect of N-octylamine on the cytochrome b5 spectrum of insect and mammalian microsomes [17].
• Participation of cytochrome b5 in CMP-N-acetylneuraminic acid hydroxylation in mouse liver cytosol [18].
• The subcellular fractions of the resistant cells showed decreased contents of MFO components, cytochrome P-450 and cytochrome b5, in comparison with the identically prepared fractions of the parental tumor [19].

Associations of Cyb5 with chemical compounds

• Cytochrome b5 stimulates the coumarin 7-hydroxylation activity of P450coh [10].
• A variety of electron acceptors have been compared as to rate with the following result: ferricyanide greater than cytochrome c greater than cytochrome b5 greater than glyoxylate greater than dichlorophenolindophenol [20].
• Cytochrome b5 content and NADH-ferricyanide reductase activity were unchanged at 30 and 300 mg/kg of CS2, although NADH-cytochrome c reductase activity was increased at the latter dose [21].
• The present study reports the modulatory influence of alcoholic extract from the leaves of Ocimum sanctum on the activities of cytochrome p-450, cytochrome b5, and aryl hydrocarbon hydroxylase enzymes in the liver and glutathione-S-transferase and reduced glutathione level in the liver, lung, and stomach of the mouse [22].
• The partitioning of cytochrome b5 in aqueous two-phase systems of polyethylene glycol (PEG) and potassium phosphate salts was investigated [23].
• For some drugs, the pharmacokinetics were also markedly altered; for example, when administered orally, the maximum plasma concentration for midazolam was increased by 2.5-fold, and the clearance decreased by 3.6-fold in hepatic microsomal cytochrome b5 null mice [24].

Other interactions of Cyb5

• OA produced a dose-dependent reduction in liver microsomal cytochrome P450 (P450) levels (25-37%) and cytochrome b5 (15-21%) content, but had no effect on NADPH-cytochrome c reductase activity [25].
• Dams receiving mace treatment and their F1 pups showed significantly elevated hepatic sulfhydryl content, glutathione S-transferase and glutathione reductase activities and cytochrome b5 content [26].
• However, the measurement of microsomal marker enzyme activities (cytochrome b5 and glucose-6-phosphatase) showed significant elevation [27].
• Our findings implicate P450 reductase, cytochrome b5 reductase, and cytochrome b5 in the activation of the compound [28].
• Neither cytochrome b5 nor NADPH-cytochrome P-450 reductase is affected [29].

Analytical, diagnostic and therapeutic context of Cyb5

• Several distinct saponins, designated QS-7, QS-17, QS-18, and QS-21, were demonstrated to boost antibody levels by 100-fold or more when used in mouse immunizations with the Ag BSA and beef liver cytochrome b5 [30].

References