Abstract
Dolichyl phosphate is an intermediate in the glycosylation of N-glycosamidic linked glycoproteins in mammalian systems, and its availability may be a limiting factor in glycoprotein biosynthesis. The basic kinetics and subcellular distribution of enzymes which may influence the concentration of dolichyl phosphate in rat liver have therefore been investigated. These include dolichyl phosphate phosphatase, dolichol phosphokinase, dolichyl fatty acyl ester synthetase, GDP-mannose dolichyl phosphate mannosyl transferase, and UDP-glucose dolichyl phosphate glucosyl transferase. The specific activity of the enzymes was highest in the microsomes, except for dolichyl phosphate phosphatase and dolichyl fatty acyl ester synthetase, which were most concentrated in the plasma membrane and the cytosol fraction, respectively. The nuclei contained all of the enzyme activities while the mitochondria and cytoplasm were generally less active. The presence of both dolichol phosphokinase and dolichyl phosphate phosphatase in microsomes and nuclei, which contain the highest glycosyl transferase activities, may provide a means for direct enzymatic control of levels of dolichyl phosphate.
Highlights
Dolichyl phosphate is an intermediate in the glyco- study,the kinetics of each of thesereactions except the sylation ofN-glycosamidiclinkedglycoproteinsin recently described dolichyl fatty acyl ester esterase [16] has mammalian systems, and its availabilitymay be a lim- been determined to establish suitacbolneditions for measuring iting factor in glycoprotein biosynthesis
Since the mass of [l-JH]dolichol was both dolichol phosphokinase and dolichyl phosphate negligible, 1-propanol was added as a carrier which could be phosphatase in microsomes and nuclei, which contain the highest glycosyl transferase activities, may provide a means for direct enzymatic control oflevels of dolichyl phosphate
Dolichyl phosphate phosphatase activitywas detected with the assay conditions described under “Materials and Methods,” which were basedon a more detailed characterizationof the enzymatic activity [11].Phosphatase activity was linear with respect to time(Fig. L 4 ) and protein concentration(Fig
Summary
From the Departmentof Biochemistry, University of Western Ontario, London, Ontario, Canada N6A 5Cl. Dolichyl phosphate is an intermediate in the glyco- study,the kinetics of each of thesereactions except the sylation ofN-glycosamidiclinkedglycoproteinsin recently described dolichyl fatty acyl ester esterase [16] has mammalian systems, and its availabilitymay be a lim- been determined to establish suitacbolneditions for measuring iting factor in glycoprotein biosynthesis. The presnetics and subcellular distribution of enzymes which ence of enzymesof dolichol metabolismtogether withenzymes may influence the concentration of dolichyl phosphate of the proteinglycosylation pathway in rat liver microsomes, in rat liver have been investigated. These nuclei, and plasma membranes mayprovide a means to regpminhacolnukndinoesaesdeo,dldoicolihlciychlhyylplhpfohastoptsyhpahataceytelphemsotsaepnrhnsaoytsnaystlhe,ettrdaaosnelsi,cfGehroDalPsep-,hoaussnyl-adlatetiolenv. Els of dolichyl phosphate available for protein glyco-.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
