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NDP‐sugars, floridoside and floridean starch levels in relation to activities of UDP‐glucose pyrophosphorylase and UDP‐glucose‐4‐epimerase in Solieria chorda l is (Rhodophyceae) under experimental conditions
Author(s) -
Goulard Fabienne,
Corre Géraldine,
Diouris Marcel,
Deslandes Eric,
Floc'h JeanYves
Publication year - 2001
Publication title -
phycological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.438
H-Index - 44
eISSN - 1440-1835
pISSN - 1322-0829
DOI - 10.1046/j.1440-1835.2001.00219.x
Subject(s) - starch , biology , thallus , sugar , carbohydrate , enzyme , galactose , biochemistry , nutrient , carbohydrate metabolism , botany , ecology
SUMMARY Under limited nutrient availability (i.e. unenriched sea‐water) and under 75 mol photons m –2 s –1 irradiance 12:12 LD, thalli of Solieria chordalis J. Agardh accumulated floridean starch and floridoside. When they were transferred into nutrient‐enriched seawater (150 umol L −1 NO3 1 ‐ and 7 umol L −1 P0 4 3 i at 35 umol photons m −2 s −1 in irradiance 12:12 LD, starch and floridoside levels decreased. The main nucleotide diphosphate (NDP) sugars (i.e. UDP‐glucose, UDP‐galactose and ADP‐glucose) and the activities of UDP‐glucose pyrophosphorylase [Enzyme Code (EC) 2.7.7.9] and UDP‐glucose‐4‐epimerase (EC 5.1.3.2) were measured under these controlled culture conditions. Both UDP‐glucose and UDP‐galactose in the thal l i increased under conditions known to favor the accumulation of floridean starch and floridoside, whereas they decreased under conditions leading to floridean starch and floridoside breakdown. On the other hand, ADP‐glucose level only varied slightly. Although UDP‐glucose pyrophosphorylase activity rose under conditions of floridean starch synthesis, little variation was observed in UDP‐glucose‐4‐epimerase activity. These results suggest a possible enzymatic regulation of the NDP‐sugar and carbohydrate pool in which UDP‐glucose pyrophosphorylase would play a major role.