Novel alkaline protease M.sub.3 method for the preparation thereof and dental caries-prophylactic composition containing the same

Alkaline protease M.sub.3 which has the following chemical and physical properties:

• (1) Activities:
• It can hydrolyze casein and inhibits the activity of glucosyltransferase.
• (2) Optimum pH and pH stability:
• It has an optimum pH range of 9 to 12.5 (substrate:
• casein), and when it it kept in a buffer solution (pH 4-9) at 37.degree. C. for 6 days, about 50% or more of the protease activity is remained.
• (3) Optimum temperature and heat stability:
• it has an optimum temperature of about 65.degree. C. (substrate:
• casein), and even when an aqueous solution of this enzyme is heated at 55.degree. C. for 10 minutes, it is stable
• (4) Conditions for inactivation:
• When an aqueous solution of this enzyme is heated at 60.degree. C. for 10 minutes, about 50% of the protease activity is lost, and when the aqueous solution is heated at 65.degree. for 10 minutes, 90% or more of the activity is lost
• (5) Effects of various additives:
• The protease activity of this enzyme is completely inhibited by 10.sup.-4 M of N-bromosuccinimde, but is almost not inhibited by 10.sup.-3 M of iodoacetic acid, diisopropyl fluorophosphate, ethylenediamine tetraacetate, and FeSO.sub.4.
• (6) Isoelectric point:
• about pH 9.5
• (7) Molecular weight:
• about 1.7.times.10.sup.4.