Autor(es):
Lages, Fernanda 
; Oliveira, Rui Pedro Soares de ; Lucas, Cândida
Data: 1999
Identificador Persistente: http://hdl.handle.net/1822/2370
Origem: RepositóriUM - Universidade do Minho
Assunto(s): S. cerevisiae mutants; Glycerol metabolic pathway; Transport
Descrição
Apresentação e resumo efectuados no 17th Small Meeting on Yeast Transport and Energetics em Córdoba, Espanha de 9 a 12 de Setembro de 1999. With the purpose of studying the correlation between glycerol metabolic pathway and
glycerol active transport (1) in S. cerevisiae, an extensive study on glycerol transport
was elaborated in all the available mutants from the genes of glycerol metabolic
pathway having W303 as common genetic background: gut1∆, gut2∆, gpp1∆, gpp2∆,
gpd∆1 and gpd2∆ and several double mutants. For this purpose we chose to diagnostic
active transport determining uptake kinetic parameters (Km and Vmax) and maximum
glycerol accumulation ratios, as well as the capacity of accumulated radiolabeled
substrate to be extruded after accumulation in glucose- and ethanol-grown cells. All
these mutant strains presented active uptake of the same order of magnitude of the wild
type, except glycerol kinase deletion mutant, gut1∆. Ethanol-grown cells of gut1∆
presented active uptake with identical Km but lower Vmax (± 70%) than wild type
strain. This indicated that, most probably, uptake Vmax determinations in all the other
strains might present some contribution of glycerol kinase activity. This hypothesis was
reinforced with measurements of glycerol kinase activity in cell free extracts obtained
under the same physiological conditions. Furthermore, gut1∆ and gut2∆ glucose-grown
cells were also tested as to the activity of Fps1(2). Passive diffusion constant values
were similar to the ones in wild type cells, but Fps1 activity could not be detected in
gut1∆.
The results suggest that glycerol kinase activity, from all the enzymes in glycerol
pathway, is the only one to interfere with active uptake measurements, although it does
not resume them. The same reasoning could not be applied to Fps1 activity detection,
which is highly affected by the presence of glycerol kinase, questioning its role as a
facilitator(2) and thus opening a clear way for the clarification, instead, of its role as a
channel(3).
