The Organization and Regulation of Plant Glycolysis

Abstract

This review discusses the organization and regulation of the glycolytic pathway in plants and compares and contrasts plant and nonplant glycolysis. Plant glycolysis exists both in the cytosol and plastid, and the parallel reactions are catalyzed by distinct nuclear-encoded isozymes. Cytosolic glycolysis is a complex network containing alternative enzymatic reactions. Two alternate cytosolic reactions enhance the pathway's ATP yield through the use of pyrophosphate in place of ATP. The cytosolic glycolytic network may provide an essential metabolic flexibility that facilitates plant development and acclimation to environmental stress. The regulation of plant glycolytic flux is assessed, with a focus on the fine control of enzymes involved in the metabolism of fructose-6-phosphate and phosphoenolpyruvate. Plant and nonplant glycolysis are regulated from the "bottom up" and "top down," respectively. Research on tissue- and developmental-specific isozymes of plant glycolytic enzymes is summarized. Potential pitfalls associated with studies of glycolytic enzymes are considered. Some glycolytic enzymes may be multifunctional proteins involved in processes other than carbohydrate metabolism.

Routes of pyruvate synthesis in phosphorus‐deficient lupin roots and nodules

“…The activities of the PEPc reaction can lead to the synthesis of malate via MDH (Duff et al, 1989;Plaxton, 1996) and although malate is a known inhibitor of PEPc activity (Schuller & Werner, 1993), there was no consistent relationship between malate concentration and the inhibition of in vitro PEPc activity. Instead, our in vitro PEPc activity varied with the P levels, as proposed by previous studies (Duff et al, 1989;Theodorou & Plaxton, 1993;Juszczuk & Rychter, 2002).…”

In Vivo Respiratory Metabolism of Illuminated Leaves

“…In addition, photorespiratory produced NH 3 is also assumed to inhibit this enzyme (Krö mer, 1995). By contrast, the chloroplastic PDH is not regulated by phosphorylation and is assumed to be active in the light (Plaxton, 1996). The decarboxylation rate measured in this study (Table I) is likely to be the sum of both PDH activity in which the chloroplastic enzyme plays the major role.…”

“…In darkness, leaves no longer assimilate CO 2 via the photosynthetic carbon reduction cycle but produce CO 2 through dark respiration. Although dark respiration is known to involve glycolysis and CO 2 production through pyruvate dehydrogenation and the degradative Krebs cycle (Trethewey and ap Rees, 1994;Plaxton, 1996), the carbon metabolism that is responsible for the CO 2 respiratory release in the light is almost unknown. This is so because the day respiratory CO 2 flux is very low and masked by the photosynthetic carbon fixation and the photorespiratory CO 2 production in the light, and is thus difficult to study.…”

Molecular cloning and biochemical characterization of three phosphoglycerate kinase isoforms from developing sunflower (Helianthus annuus L.) seeds

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 and the other in plastids (pPGK) (Anderson and Advani, 1970). The cytosolic enzyme functions primarily in glycolysis for substrate-level ATP generation, one of the two glycolytic steps that produce ATP (Plaxton, 1996), and is also involved in gluconeogenesis. The plastidial isoform is involved in the photosynthetic carbon reduction cycle and in chloroplast glycolysis.…”