Mechanism of killing bacteria, expression of gene encoded enzyme and its genetics

用凝胶过滤柱层析分离小鼠乳中的L氨基酸氧化酶和乳过氧化物酶，L氨基酸存在下产生H_2O_2，L PO在H_2O_2的降解过程中产生O。牛奶中的H_2O_2能产生细菌毒性的H_2O_2和O，H_2O_2的生成量约为300Mole/ml牛奶。为了研究LAO和LPO是否起到杀灭乳腺细菌的作用，从牛乳房炎乳汁中分离出细菌(大肠杆菌、肺炎克雷伯菌、金黄色葡萄球菌和无乳链球菌)，并在有或没有LPO的情况下与LAO一起培养。在L氨基酸存在下，LAO抑制肺炎克雷伯菌和大肠杆菌的生长，杀灭金黄色葡萄球菌。无乳链球菌在LAO存在下正常生长，在LAO和LPO存在下不生长。因此，我们将它们分为两类：一类是H_2O_2敏感的，另一类是O^敏感的。结论：乳汁中产生的H_2O_2和O~-对小鼠乳腺内细菌的生长有抑制作用。H_2O_2产生酶的峰含量为75，相对分子质量约为10K。两个品种的洗脱图谱相同。这种酶在乳汁中的含量在哺乳期早期和哺乳期后期较少，但在哺乳期中期相对较高。37℃孵育2小时，酶产生H_2O_2的量约为0小时的5倍。

L-Amino acid oxidase (LAO) and lactoperoxidase (LPO) of mouse milk are separated by gel-filtration chromatography.LAO generates H_2O_2 in the presence of L-amino acids and subsequently, LPO generates O through the degradation of H_2O_2. Milk is capable of producing the bacterial toxic H_2O_2 and O The quantity of H_2O_2 was around 300 μmoles/ml milk. In order to examine whether or not LAO and LPO is responsible for killing bacteria in the mammary gland, bacteria (Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and Streptococcus agalactiae) are isolated from bovine mastitis milk and cultured with LAO in the presence and absence of LPO. In the presence of L-amino acids, LAO inhibits the growth of Klebsiella pneumoniae and Escherichia coli, and kills Staphylococcus aureus. Streptococcus agalactiae grows normally in the presence of LAO and does not grow in the presence of LAO and LPO. Thus, we divide them into two types : one being H_2O_2-sensitive and the other being O^-sensitive. It is concluded that H_2O_2 and O^-generated in milk is able to prevent the growth of bacteria in the mouse mammary gland.Cow milk of Holstein and Japanese Black breeds are collected and separated by gel-filtration chromatography. The H_2O_2 generating enzyme is appeared at the peak fraction of 75, being a molecular weight of about 10 k. The eluting profiles of the two breeds are identical. The quantity.of this enzyme in milk is small at early lactation and at late lactation, but is relatively high at mid-lactation. By the incubation for 2 hr at 37℃, the enzyme generates H_2O_2 about 5-fold as compared to that of the 0 hr-incubation.