Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1) A Bence-Jones type protein (Cryo-Ver) showing the cold precipitation phenomenon has an extremely low intrinsic fluorescence when excited at 280-295 nm. 2) This fluorescence increases considerably upon denaturation of the molecule by heat or guanidine hydrochloride. Guanidine is about twice as effective as heat in terms of fluorescence yield. 3) The heat-denatured protein is still reactive with anti-cryoVer antibodies, at variance with the guanidine-treated samples. 4) Since the protein contains two tryptophans per mole, one in the constant portion of the molecule, the other in the variable region, it is proposed that heat treatment affects only the variable region, which seems involved in the cryoprecipitation phenomenon.
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PMID:Differential denaturation of a crystalline Bence-Jones type cryoprotein as monitored by fluorescence. 27 39

To elucidate the strategy of low temperature adaptation for a cold-adapted family 8 xylanase, the thermal and chemical stabilities, thermal inactivation, thermodependence of activity and conformational flexibility, as well as the thermodynamic basis of these processes, were compared with those of a thermophilic homolog. Differential scanning calorimetry, fluorescence monitoring of guanidine hydrochloride unfolding and fluorescence quenching were used, among other techniques, to show that the cold-adapted enzyme is characterized by a high activity at low temperatures, a poor stability and a high flexibility. In contrast, the thermophilic enzyme is shown to have a reduced low temperature activity, high stability and a reduced flexibility. These findings agree with the hypothesis that cold-adapted enzymes overcome the quandary imposed by low temperature environments via a global or local increase in the flexibility of their molecular edifice, with this in turn leading to a reduced stability. Analysis of the guanidine hydrochloride unfolding, as well as the thermodynamic parameters of irreversible thermal unfolding and thermal inactivation shows that the driving force for this denaturation and inactivation is a large entropy change while a low enthalpy change is implicated in the low temperature activity. A reduced number of salt-bridges are believed to be responsible for both these effects. Guanidine hydrochloride unfolding studies also indicate that both family 8 enzymes unfold via an intermediate prone to aggregation.
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PMID:Activity, stability and flexibility in glycosidases adapted to extreme thermal environments. 1269 50