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

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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.