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. 1981 Apr;67(4):780–784. doi: 10.1104/pp.67.4.780

Submitochondrial Location and Electron Transport Characteristics of Enzymes Involved in Proline Oxidation

Thomas E Elthon 1, Cecil R Stewart 1
PMCID: PMC425772  PMID: 16661754

Abstract

Isolated corn mitochondria (Zea mays cv. B73 × Mo17) were fractionated and the fragments were separated on a 20-45% (weight/weight) continuous sucrose gradient. Soluble enzymes remained at the top of the gradient overlapping with the outer membranes, while inner membrane vesicles and intact inner membranes were distributed farther down the gradient. Proline oxidase and Δ1-pyrroline-5-carboxylic acid dehydrogenase activities were associated only with the inner mitochondrial membrane. Glutamate dehydrogenase was confirmed as a matrix enzyme.

Both proline and Δ1-pyrroline-5-carboxylic acid supported oxygen uptake in isolated mitochondria. Proline dependent oxygen uptake was relatively independent of pH with a maximum rate at pH 7.2. In contrast, Δ1-pyrroline-5-carboxylic acid-dependent oxygen uptake was sensitive to pH with an optimum at pH 6.1. The oxidation of proline and Δ1-pyrroline-5-carboxylic acid was inhibited by 10 micromolar rotenone. This indicates that electrons from these substrates enter the respiratory chain prior to at least one of the rotenone sensitive iron-sulfur proteins. Both substrates yielded ADP:O ratios of around 1.9 as compared to malate plus pyruvate (2.1), succinate (1.3), and exogenous NADH (1.2).

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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