Hydrogenase activity in the dry state

Yagi, Takeshi; Tsuda, Masami; Mori, Yasushige; Inokuchi, Hiroo

doi:10.1021/ja01038a074

Cited by 37 publications

(17 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There is good evidence from work on enzyme catalysis in dry organic solvents that activity may be possible at very low hydrations 29,30 , but interpretation of this work is complicated by the likelihood that the organic solvent is replacing water at sites on the enzyme, as well as performing a hydration function by loosening the structure 31,32 . However, hydrogenase activity has been observed in the dry state 33 , and we have observed enzyme activity in milk powders at < 0.06 h 34 .…”

Section: Enzyme Hydrationmentioning

confidence: 59%

Astroenzymology - the environmental limits of enzyme activity

Daniel

2003

Instruments, Methods, and Missions for Astrobiology V

View full text Add to dashboard Cite

Using organisms from extreme terrestrial environments as models for extraterrestrial life may lead us to underestimate the range of environments that life may inhabit. An alternative approach is to inspect the range of conditions over which crucial biomolecules might function. Recent investigations of enzyme activity suggest that they have the potential to function over a wider range of environmental conditions than expected. Although the upper temperature limit for enzyme stability is unclear, some enzymes are active up to 130 o C. The evidence is that that the instability of enzymes is a functional requirement, rather than because of any restraint on achieving higher stability. There is no evidence that enzyme activity ceases at low temperatures; it declines in a predictable manner to the lowest temperature at which it has been possible to make measurements, -100 o C. It has been generally accepted that dehydration stops enzyme activity but this acceptance may have arisen partly from the technical difficulty of assessing enzyme activity without a fluid medium for diffusion. Experiments using anhydrous organic solvents or gas phase substrates suggest activity occurs in enzymes at very low hydration.

show abstract

Section: Enzyme Hydrationmentioning

confidence: 59%

Astroenzymology - the environmental limits of enzyme activity

Daniel

2003

Instruments, Methods, and Missions for Astrobiology V

View full text Add to dashboard Cite

show abstract

“…One of the earliest reports of this method was by Yagi et al (1969), who investigated the activity of freeze-dried hydrogenase from Desulfovibrio desulfuricans. They observed that the dry enzyme still catalysed the conversion of ortho-H 2 to para-H 2 .…”

Section: Gas-phase Dry Enzyme Activity Resultsmentioning

confidence: 99%

The use of gas–phase substrates to study enzyme catalysis at low hydration

Dunn

Daniel

2004

Phil. Trans. R. Soc. Lond. B

View full text Add to dashboard Cite

Although there are varying estimates as to the degree of enzyme hydration required for activity, a threshold value of ca. 0.2 g of water per gram of protein has been widely accepted. The evidence upon which this is based is reviewed here. In particular, results from the use of gas-phase substrates are discussed. Results using solid-phase enzyme-substrate mixtures are not altogether in accord with those obtained using gasphase substrates. The use of gaseous substrates and products provides an experimental system in which the hydration of the enzyme can be easily controlled, but which is not limited by diffusion.All the results show that increasing hydration enhances activity. The results using gas-phase substrates do not support the existence of a critical hydration value below which enzymatic activity is absent, and suggest that enzyme activity is possible at much lower hydrations than previously thought; they do not support the notion that significant hydration of the surface polar groups is required for activity. However, the marked improvement of activity as hydration is increased suggests that water does play a role, perhaps in optimizing the structure or facilitating the flexibility required for maximal activity.

show abstract

“…The apparent activation energy for the reaction catalyzed by the lyophilized enzyme in the dry state was 7.5 kcal/mole, and that in solution was 11.8 kcal/mole. 31 Finally, in the hydration of carbon dioxide by carbonic anhydrase, the carbon dioxide is not distorted but hydroxide appears to be far more reactive than in solution.32 Part of the energy of binding of carbon dioxide may be utilized to separate with it a hydroxide ion from bulk water. Reaction of hydroxide in water requires substantial activation energy for separation of a hydroxide ion from a water shell.33…”

Section: +mentioning

confidence: 99%

Active Site of α-Chymotrypsin Activation by Association-Desolvation

Cohen

Vaidya

Schultz

1970

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Abstract. High reactivity toward a-chymotrypsin is observed for derivatives of f3-arylpropionic acids of varied structure-L-a-acylamido compounds, Dcyclized compounds, and, now, L-glycolamide esters. Compensating enthalpy and entropy effects are observed which appear to be caused by changes in water of solvation. High reactivity with varied structure, and physical evidence, appear to rule out induced fit and distortion as important for this enzyme. The high reactivity results from precise fit of the hydrolyzing group at the critical serine-imidazole junction, resulting from binding of the aryl group and restriction of rotation. Part of the energy of binding is used to desolvate the reactant groups of substrate and enzyme, decreasing activation energies by several kilocalories and raising reactivity by 103 or more. Solvation by water stabilizes many compounds, allowing them to be present in solution in biological systems. Their reactions may occur as their reactivity is increased when they are desolvated and brought from solution into association with reactive groups in enzymes, membranes, and structured particles.The active site of a-chymotrypsin has been described as composed of parts complementary to the parts of a reactive substrate, L-methyl N-acetylphenylalaninate, C6HCH2CH(NHCOCH3)CO2CHs, compound I-A, in a conformation in which the ,6-aryl and hydrolyzing ester groups are transoid' 2 (Fig. 1). The parts are (a) ar, a cavity in which the f3-aryl group provides the primary associative effect, which leads to efficient binding, low Ki, and contributes to favorable kinetic constant, kcat;"34 (b) am, at or near the enzyme surface, to which the aacylamido group associates by hydrogen bonding, leading to high kcat,' particularly but not only when Km is favorable,6 but not of itself leading to low K.;7 (c) h, a part of restricted volume, contiguous with ar, into which the a-hydrogen or a small polar substituent may fit;8 (d) n, the hydrolytic part, at or near the surface and including the hydroxyl of serine-1959 and imidazole of histidine-57.10 249

show abstract

Hydrogenase activity in the dry state

Cited by 37 publications

References 0 publications

Astroenzymology - the environmental limits of enzyme activity

Astroenzymology - the environmental limits of enzyme activity

The use of gas–phase substrates to study enzyme catalysis at low hydration

Active Site of α-Chymotrypsin Activation by Association-Desolvation

Contact Info

Product

Resources

About