    1.5.99.B2 | physiological function |
proline (Pro) dehydrogenase (ProDH) catalyzes the rate limiting step in the oxidation pathway, transferring two electrons from Pro to the noncovalently bound FAD cofactor to subsequently deliver these electrons to a final acceptor. The plant enzyme sustains oxidative phosphorylation and ATP generation using endogenous electron acceptors. ProDH potentiates the oxidative burst and cell death of the plant hypersensitive response. ProDH converts Pro into DELTA1 pyrroline-5-carboxylate (P5C) and can act together with P5C dehydrogenase (P5CDH) to produce Glu, or with P5C reductase (P5CR) to regenerate Pro and thus stimulate the Pro/P5C cycle. ProDH activation has different effects on hypersensitive response. Before the oxidative burst it leads to Pro consumption involving the action of P5CDH. During the oxidative burst, ProDH becomes functionally uncoupled to P5CDH and apparently works with P5C reductase. The absence of P5CDH does not reduce reactive oxygen species, cell death, or pathogen resistance, indicating this enzyme is not accompanying ProDH in the potentiation of these defense responses. In contrast, p5cdh infected mutant plants display increased reactive oxygen species burst and earlier initiation of hypersensitive response cell death. ProDH may sustain hypersensitive response by participating in the Pro/P5C cycle. Evaluation of ProDH action at different hypersensitive response stages, overview |
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