Catalytic activity of cytochrome oxidase and cytochrome c in apolar solvents containing phospholipids and low amounts of water

Escamilla, Edgardo; Ayala, Guadalupe; Gómez‐Puyou, Marietta Tuena de; Gómez‐Puyou, Armando; Millán, Lourdes; Darszon, Alberto

doi:10.1016/0003-9861(89)90227-0

Cited by 21 publications

(15 citation statements)

References 41 publications

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“…At least two factors may contribute to the increased reduction of mitochondrial Cyts: (a) the lack of O 2 , as suggested by studies of mammalian (Kariman et al, 1983), fungal (Leštan et al, 1993), and plant tissues (Lance and Bonner, 1968), and (b) viscosity that changes the solvent properties around COX (Escamilla et al, 1989;Kornblatt and Hoa, 1990). However, the interpretation of the COX redox behavior in our material during drying is further complicated because O 2 availability is also related to viscosity.…”

Section: Effects Of O 2 Supply On Cox Reduction During Dryingmentioning

confidence: 87%

“…Such water movements can be inhibited by decreasing water activity or osmotic potential, which results in the reduction of the Cyt a (Escamilla et al, 1989;Kornblatt and Hoa, 1990). To test whether a decreased water activity in the cotyledons caused the reduction of Cyt a, we compared the A 599-603 from material dried at 22°C and 5°C (Fig.…”

Section: Relation Among Viscosity Temperature and Redox State Of Coxmentioning

confidence: 99%

“…For instance, it has been shown that the reduction of O 2 by COX is inhibited in conditions that prevent the solvent entry and expulsion between Cyt a and Cyt a 3 during the COX catalytic cycle (Escamilla et al, 1989;Kornblatt and Kornblatt, 1992). Such water movements can be inhibited by decreasing the water activity of the medium (Kornblatt and Hoa, 1990).…”

Section: Impeded O 2 Diffusion Is a Likely Factor Responsible For Thementioning

confidence: 99%

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The Responses of Cytochrome Redox State and Energy Metabolism to Dehydration Support a Role for Cytoplasmic Viscosity in Desiccation Tolerance

Leprince

Hoekstra

1998

Plant Physiology

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To characterize the depression of metabolism in anhydrobiotes, the redox state of cytochromes and energy metabolism were studied during dehydration of soaked cowpea (Vigna unguiculata) cotyledons and pollens of Typha latifolia and Impatiens glandulifera. Between water contents (WC) of 1.0 and 0.6 g H 2 O/g dry weight (g/g), viscosity as measured by electron spin resonance spectroscopy increased from 0.15 to 0.27 poise. This initial water loss was accompanied by a 50% decrease in respiration rates, whereas the adenylate energy charge remained constant at 0.8, and cytochrome c oxidase (COX) remained fully oxidized. From WC of 0.6 to 0.2 g/g, viscosity increased exponentially. The adenylate energy charge declined to 0.4 in seeds and 0.2 in pollen, whereas COX became progressively reduced. At WC of less than 0.2 g/g, COX remained fully reduced, whereas respiration ceased. When dried under N 2 , COX remained 63% reduced in cotyledons until WC was 0.7 g/g and was fully reduced at 0.2 g/g. During drying under pure O 2 , the pattern of COX reduction was similar to that of air-dried tissues, although the maximum reduction was 70% in dried tissues. Thus, at WC of less than 0.6 g/g, the reduction of COX probably originates from a decreased O 2 availability as a result of the increased viscosity and impeded diffusion. We suggest that viscosity is a valuable parameter to characterize the relation between desiccation and decrease in metabolism. The implications for desiccation tolerance are discussed.

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Section: Effects Of O 2 Supply On Cox Reduction During Dryingmentioning

confidence: 87%

Section: Relation Among Viscosity Temperature and Redox State Of Coxmentioning

confidence: 99%

Section: Impeded O 2 Diffusion Is a Likely Factor Responsible For Thementioning

confidence: 99%

See 1 more Smart Citation

The Responses of Cytochrome Redox State and Energy Metabolism to Dehydration Support a Role for Cytoplasmic Viscosity in Desiccation Tolerance

Leprince

Hoekstra

1998

Plant Physiology

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“…The fact that the micelles containing the ATPase are easily sedimented at relatively low centrifugation speeds suggests a mechanism of micellar aggregation. The type of aggregates formed remains to be determined as well as whether the two extremities lie in the same or in neighbouring micelles (Ramakrishnan et al, 1983;Escamilla et al, 1989;Bru et al, 1989;Luisi and Magid, 1986). This work has shown that an ATPase of the P-type can carry out catalysis when entrapped in reverse micelles.…”

Section: Discussionmentioning

confidence: 99%

Are there different water requirements in different steps of a catalytic cycle?

Barrabin

Scofano

Gómez‐Puyou

et al. 1993

European Journal of Biochemistry

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The Ca2+-ATPase from sarcoplasmic reticulum was transferred in an active form to a low-water system composed of toluene, phospholipids, and Triton X-100 (TPT). The Ca2+-ATPase activity in the TPT system with 4.0% water (by vol.) was about 50% of the activity observed in all-aqueous mixtures. Phosphate formation was linear with time up to 20% of ATP hydrolysis and, as expected from an enzyme-catalysed reaction, activity was linear with protein concentration. No ATPase activity was detected in the presence of 3 mM EGTA, indicating that the enzyme retained its Ca2+ dependence in the TPT system. A hyperbolic response to ATP concentration was observed with a K , of 0.15 mM. There was no detectable ATPase activity at water concentrations below 1.5% (by vol.). With 2.0% water, activity became detectable and increased as the water content was progressively raised to 7.0% (by vol.). Higher amounts of water produced unstable emulsions. Enzyme phosphorylation by ATP and dephosphorylation took place in the TPT system. The velocities of both enzyme phosphorylation and dephosphorylation increased with increments in the water content. The enzyme could also be phosphorylated in the TPT system by inorganic phosphate. However, in comparison to ATP, phosphorylation by phosphate took place with significantly lower amounts of water. It is suggested that at low amounts of water, the enzyme is in a relatively rigid conformation and, as the water content is increased, the ATPase acquires more flexibility and, hence, the capacity to carry out catalysis at higher rates. Nevertheless, the release of conformational constraints of the catalytic site of the E, conformer takes place at water concentrations much lower than those needed for the expression of catalytic activity by the E, conformer.A considerable amount of work has accumulated on the behavior of enzymes in systems formed predominantly with organic solvents. The studies have been carried out with enzymes dispersed in the solvent (Klibanov, 1983(Klibanov, , 1989 or entrapped in the interior of reverse micelles (Martinek et al., 1986;Luisi and Magid, 1986;Walde et al., 1990). One of the salient features of enzymes in either of the two conditions is that, when they are in contact with low amounts of water, they exhibit a high thermostability (Garza-Ramos et al., 1989; Ayala et al., 1986; Zacks and Klibanov, 1984, 1988;Wheeler and Croteau, 1986) and low catalytic rates (GarzaRamos et al., 1989(GarzaRamos et al., , 1990(GarzaRamos et al., , 1992a. It has been proposed that these two phenomena result from restrictions in enzyme conformational mobility as imposed by the low-water environment (for review see Garza-Ramos et al., 199213 mational changes, it should be possible to stabilize particular enzyme conformations by varying the amount of water in contact with the enzyme. Studies along this line could also shed light on solvent-protein interactions that occur during catalysis, in particular if different steps of the catalytic cycle have distinct and defined water requeriments. The ...

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“…A number of recent papers have dealt with the properties of membrane-associated proteins in phosphatidylcholine-based microemulsions. Examples include enzymes of the mitochondria] respiratory electron transfer chain (Escamilla et al, 1989;Escobar and Escamilla, 1992) and FcATPase in the phospholipid toluene water system (Garza-Ramos et al, 1989). These studies, which may be regarded as preliminary, indicate that the intact respiratory chain can be made to function in microemulsions.…”

Section: Microemulsions As Membrane-mimetic Systemsmentioning

confidence: 97%

Enzymes in Water-in-oil Microemulsions (‘Reversed Micelles’): Principles and Applications

Oldfield¹

1994

Biotechnology and Genetic Engineering Reviews

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Catalytic activity of cytochrome oxidase and cytochrome c in apolar solvents containing phospholipids and low amounts of water

Cited by 21 publications

References 41 publications

The Responses of Cytochrome Redox State and Energy Metabolism to Dehydration Support a Role for Cytoplasmic Viscosity in Desiccation Tolerance

The Responses of Cytochrome Redox State and Energy Metabolism to Dehydration Support a Role for Cytoplasmic Viscosity in Desiccation Tolerance

Are there different water requirements in different steps of a catalytic cycle?

Enzymes in Water-in-oil Microemulsions (‘Reversed Micelles’): Principles and Applications

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