ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
Administration of radioactively labeled galactose to cultured mammalian cells brings about an accumulation of metabolic products the pattern of which seems to be governed by a variety of vectors in the intracellular milieu. By manipulation of culture conditions some of these vectors appear to be a function of glycolysis. In the non-glycolytic culture, label from a galactose probe appears as Galactose-1-phosphate (Gal-1-P) and UDPglucuronic acid (UDPGlcUA). Conversely, glycolytic culture conditions seem not to permit the formation to UDPGlcUA since the only labeled accumulation product formed was UDPHex. A suggestion is made that the difference in metabolic activity of glucose-fed and glucose-starved cultures may be related to the effect of NADH on the in situ activity of UDPG dehydrogenase (UDPglucose:NAD oxidoreductase, E.C. 1.1.1.22) (abbreviation, UDPG-DH). This prompted an investigation of the effects of NAD and NADH on the activity of partially purified UDPG-DH. The results of these experiments strongly suggest that the activity of UDPG-DH (in situ) is negatively controlled by increased levels of NADH; the latter condition is known to exist in glycolytically active cells (Schwartz and Johnson, 1976). Added to this is a second control mechanism which is characterized by a transient inhibition of uridylyltransferase (UDP glucose:α-D-galactose-1-phosphate uridylyltransferase, E.C. 2.7.7.12). Since it is known that there is little, if any, effect on galactokinase (ATP:D-galactose-1-phosphotransferase, E.C. 2.7.1.6) activity as a result of sugar starvation (Christopher et al., 1976), the low in vivo activity of uridylyltransferase contributes not only to the increased accumulation of Gal-1-P but also to a drastic decrease of labeled UDPhexoses, although the pre-existing pool of UDPhexose was found to decrease only moderately under the condition of glucose starvation (30% still persisted). The benefit of this type of control is not clear.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1040960104
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