Messer M, Elliott C
Department of Biochemistry, University of Sydney, N.S.W.
Aust J Biol Sci. 1987;40(1):37-46.
alpha-Lactalbumin was isolated from milk of M. eugenii and its concentration in milk samples taken at various times during lactation (0-40 weeks post partum) was determined by single radial immunodiffusion using rabbit antiserum to the purified protein. The alpha-lactalbumin concentration remained almost constant throughout lactation even though the concentration of total lactose (free lactose plus lactose contained in oligosaccharides) fell to zero after 34 weeks post partum. This fall in lactose was accompanied by a rise in the free galactose and glucose concentrations and marked increases in UDP-galactose hydrolase, nucleotide pyrophosphatase, alkaline phosphatase and acid beta-galactosidase activities. It is suggested that the in vitro hydrolysis of UDP-galactose was due to nucleotide pyrophosphatase and that this enzyme may also play a role in vivo late in lactation by making UDP-galactose unavailable for the synthesis of lactose. Alternatively, lactose and lactose-containing oligosaccharides might be degraded by the acid beta-galactosidase during or after secretion.
从尤金氏负鼠（M. eugenii）的乳汁中分离出α-乳白蛋白，并使用针对纯化蛋白的兔抗血清，通过单向辐射免疫扩散法测定了泌乳期间（产后0 - 40周）不同时间采集的乳汁样本中α-乳白蛋白的浓度。尽管产后34周后总乳糖（游离乳糖加上低聚糖中所含乳糖）的浓度降至零，但整个泌乳期α-乳白蛋白的浓度几乎保持恒定。乳糖的这种下降伴随着游离半乳糖和葡萄糖浓度的升高，以及UDP-半乳糖水解酶、核苷酸焦磷酸酶、碱性磷酸酶和酸性β-半乳糖苷酶活性的显著增加。有人认为，UDP-半乳糖的体外水解是由于核苷酸焦磷酸酶引起的，并且这种酶在泌乳后期的体内可能也发挥作用，使UDP-半乳糖无法用于乳糖的合成。或者，乳糖和含乳糖的低聚糖可能在分泌过程中或分泌后被酸性β-半乳糖苷酶降解。
