Skip to page content
USDA Forest Service

Research & Development Treesearch

Treesearch Home
About Treesearch
Contact Us
Research & Development
Forest Products Lab
International Institute of Tropical Forestry
Pacific Northwest
Pacific Southwest
Rocky Mountain
Southern Research Station
Help - We Participate  Government Made Easy

Global Forest Information Service

US Forest Service
P.O. Box 96090
Washington, D.C.

(202) 205-8333

You are here: Home / Search / Publication Information
Bookmark and Share

Publication Information

View PDF (0 bytes)

Title: Regulations and roles for alternative pathways of hexose metabolism in plants

Author: Black, Clanton C.; Mustardy, Laszlo; Sung, S.S.; Kormanik, P.P.; Xu, D.-P.; Paz, Nachman;

Date: 1987

Source: Physiologia Plantarum. 69: 387-394

Publication Series: Scientific Journal (JRNL)

Description: Plants have two cytoplasmic pathways of glycolysis and gluconeogenesis for the reversible interconversion of fructose 6-phosphate (F-6-P) and fructose 1,6-bisphosphate (F-1,6,-P2). One pathway is described as a maintenance pathway that is catalyzed by a nucleotide triphosphate-dependent phosphofructokinase (EC; ATP-PFK) glycolytically and a F-1,6 bisphosphatase (EC gluconeogenically. These are non-equilibrium reactions that are energy consuming. The second pathway, described as an adaptive pathway, is catalyzed by a readily reversible pyrophosphate-dependent phosphofructokinase (EC; PPi-PFK) in an equilibrium reaction that conserves energy through the utilization and the synthesis of pyrophosphate. A constitutive regulator cycle is also present for the synthesis and hydrolysis of fructose 2,6-bisphosphate (F-2,6-P2) via a 2-kinase and a 2-phosphatase, respectively. The pathway catalyzed by ATP-PFK and F-1,6-bisphosphatase, the maintenance pathway, is fairly constant in maximum activity in various plant tissues and shows less regulation by F-2,6-P2. Plants use F-2,6-P2 initially to regulate the adaptive pathway at the reversible PPi-PFK step. The adaptive pathway, catalyzed by PPi-PFK, varies in maximum activity with a variety of phenomena such as plant development or changing biological and physical environments. Plants can change F-2,6-P2 levels rapidly, in less than 1 min when subjected to rapid environmental change, or change levels slowly over periods of hours and days as tissues develop. Both types of change enable plants to cope with the environmental and developmental changes that occur during their lifetimes. The two pathways of sugar metabolism can be efficiently linked by the cycling uridylates and pyrophosphate required for sucrose breakdown via a proposed sucrose synthase pathway. The breakdown of sucrose via the sucrose synthase pathway requires half the net energy of breakdown via the invertase pathway. Pyrophosphate occurs in plant tissues as a substrate pool for biosynthetic reactions such as the PPi-PFK or uridine diphosphate glucose pyrophosphorylase (EC; UDPG pyrophosphorylase) that function in the breakdown of imported sucrose. Also pyrophosphate links the two glycolytic/gluconeogenic pathways; and in a reciprocal manner pyrophosphate is produced as an energy source during gluconeogenic carbon flow from F-1,6,P2 toward sucrose synthesis.

Keywords: F-6-P, F-2, 6-P2, F-1, 6-P2, glycolysis, gluconeogenesis, invertase, pyrophosphate, sucrose breakdown, sucrose synthase, UDP-glucose pyrophosphorylase

Publication Notes:

  • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.



Black, Clanton C.; Mustardy, Laszlo; Sung, S.S.; Kormanik, P.P.; Xu, D.-P.; Paz, Nachman. 1987. Regulation and roles for alternative pathways of hexose metabolism in plants. Physiologia Plantarum. 69: 387-394. 9 p.


 [ Get Acrobat ]  Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.