A BIFUNCTIONAL ENZYME (DELTA-1-PYRROLINE-5-CARBOXYLATE SYNTHETASE) CATALYZES THE 1ST 2 STEPS IN PROLINE BIOSYNTHESIS IN PLANTS

被引:423
作者
HU, CAA
DELAUNEY, AJ
VERMA, DPS
机构
[1] OHIO STATE UNIV,DEPT MOLEC GENET,RIGHTMIRE HALL,1060 CARMACK RD,COLUMBUS,OH 43210
[2] OHIO STATE UNIV,CTR BIOTECHNOL,COLUMBUS,OH 43210
关键词
OSMOREGULATION; NITROGEN ASSIMILATION; FUNCTIONAL COMPLEMENTATION; ROOT NODULES;
D O I
10.1073/pnas.89.19.9354
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Many plants synthesize and accumulate proline in response to osmotic stress. Despite the importance of this pathway, however, the exact metabolic route and enzymes involved in the synthesis of proline in plants have not been unequivocally identified. We report here the isolation of a mothbean (Vigna aconitifolia) cDNA clone encoding a bifunctional enzyme, DELTA1-pyrroline-5-carboxylate synthetase (P5CS), with both gamma-glutamyl kinase and glutamic-gamma-semialdehyde dehydrogenase activities that catalyzes the first two steps in proline biosynthesis. The two enzymatic domains of P5CS correspond to the ProB and ProA proteins of Escherichia coli and contain a leucine zipper in each domain, which may facilitate inter- or intramolecular interaction of this protein. The Vigna P5CS enzyme activity is feedback regulated by proline but is less sensitive to end-product inhibition than is the E. coli gamma-glutamyl kinase. The P5CS gene is expressed at high levels in Vigna leaves and is inducible in roots subjected to salt stress, suggesting that P5CS plays a key role in proline biosynthesis, leading to osmoregulation in plants.
引用
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页码:9354 / 9358
页数:5
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