Studies on the particulate lactose synthetase of mouse mammary gland and the role of α-lactalbumin in the initiation of lactose synthesis

1972 ◽  
Vol 127 (5) ◽  
pp. 741.b1-741.b1
Keyword(s):  
Mammary Gland ◽  
Mouse Mammary Gland ◽  
Lactose Synthesis

scholarly journals The role of nucleoside diphosphatase in a uridine nucleotide cycle associated with lactose synthesis in rat mammary-gland Golgi apparatus

1977 ◽  
Vol 168 (3) ◽  
pp. 423-433 ◽  
Author(s):  
N J Kuhn ◽  
A White
Keyword(s):  
Mammary Gland ◽  
Uridine Nucleotide ◽  
Lactose Synthase ◽  
Bivalent Metal Ions ◽  
Ump Kinase ◽  
Rat Mammary Gland ◽  
Lactose Synthesis ◽  
Galactose Utilization ◽  
Nucleoside Diphosphatase

1. UDP-galactose utilization by isolated Golgi vesicles or rat mammary gland synthesizing lactose causes accumulation of UMP but not UDP, although UDP is the immediate product of lactose synthase (EC 2.4.1.22). 2. This can be ascribed to a nucleoside diphosphatase (EC 3.6.1.6), specific for UDP, GDP and IDP, activated by bivalent metal ions and apparently located on the luminal face of the Golgi membrane. 3. The uridine diphosphatase activity exceeds the total galactosyltransferase activity 5-fold, and is estimated to maintain UDP at about 14 micrometer within the Golgi lumen. 4. Evidence is given that UMP, but not UDP, penetrates the membrane and that UMP is rephosphorylated to UDP by a UMP kinase located in the cytosol. 5. Golgi-cytosol relationships with respect to lactose synthesis are formulated in terms of a uridine nucleotide cycle which throws new light on the energy cost and possible regulation of lactose synthesis.

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