Effect of bestatin on the establishment of delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) and oxazolone was examined in normal and immunity-impaired mice. Administration of a low dose of bestatin (0.1 ti 100 dug/mouse) augmented DTH to SRBC and restored their impaired DTH to oxazolone. The effect of bestatin in the mouse was agedependent. Bestatin retarded the growth of slow growing solid tumors of GARDNER lymphosarcoma and IMC carcinoma and the effect was influenced by the time of the administration and the number of cells inoculated. Bestatin enhanced the antitumor action of the antitumor antibiotics, bleomycin and adriamycin. Bestatin also retarded the induction of skin cancer by 20-methylcholanthrene.Bestatin is a strong inhibitor of aminopeptidase B and leucine aminopeptidase1~4)and binds to the cell surface including lymphocytes and macrophages4~6). As reported previously6), bestatin in a wide dose range augments the establishment of delayed-type hypersensitivity to sheep red blood cells and a high dose more than I mg/mouse increases the number of cells forming IgM antibody to heterologous red blood cells in mice. Bestatin is a dipeptide, [(2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl]-Lleucine2) and has a extremely low toxicity.In this paper we report the immuno-potentiating activities of bestatin and its effect on murine transplantable tumors. Materials and MethodsMice CDF1 mice (Balb/c xDBA2, male or female, 4~ 14 weeks old) were supplied by Institute of Medical Science, University of Tokyo. C3H/He mice (female, 8 weeks old), ddY mice (female, 6 weeks old) and ICR mice (female, 8 -10 weeks old) were purchased from Shizuoka Agricultural Cooperative Association for Laboratory Animals. These mice were housed in plastic filter top cages and fed sterilized mouse pellet (MB-1, Funabashi Farm Co., Ltd. Chiba, Japan) and water ad libitum. Bestatin Bestatin (Lot. 751158TS) was prepared by Nippon Kayaku Co., Ltd. following the instruction of the authors1). This was used throughout this study. For animal experiments, bestatin was dissolved in distilled water at 1 or 4 mg/ml and diluted. Mice were given an appropriate dose of bestatin in 0.25 ml.Treatment with cyclophosphamide Cyclophosphamide ("Endoxan", Shionogi Co. Ltd., Osaka, Japan) was dissolved in distilled water at 16 mg/ml, and 0.25 ml of the solution containing 4 or 6 mg of cyclophosphamide was intraperitoneally injected to each mouse.Treatment with anti-lymphocyte serum Rabbit anti-mouse lymphocyte serum (ALS) was prepared by the method described by LEVEY and

Two proteinases (I and II) from a marine luminous bacterium, FLN-108, were purified to homogeneity. The molecular weights ofproteinases I and II were estimated to be 49,000 and 46,000, comprising a dimer of 23,000 molecular weight subunits, respectively. These enzymes were most active at from pH 8.0 to pH 9.0 and 50°C, and stable below 45°C. These enzyme activities were inhibited by EDTAand orthophenanthrolin.Phosphoramidon inhibited the activity of proteinase II, but not that ofproteinase I. Metal ions such as Cu2+, Hg2+, and Ni2+ strongly inhibited these activities. These results indicate that the proteinases I and II are metal-chelater-sensitive, alkaline proteinases.Wehave reported the existence of proteolytic, marine luminous bacteria, and described the purification and some properties of these enzymes from the culture supernatants of Vibrio splendidus FLE-2 and Vibrio harveyi FLA-1 1 strains.1>2) Since the proteinase activity in the culture supernatant with BGPY (basal glycerol peptone yeast extract) medium,1) which is a nutritionally complete broth, was very low, it was examined whether the enzyme activity from other Vibrio harveyi strains is also lower than that with BC(basal casein) medium,2) which lacks carbon and energy sources other than the casein. We found that several strains, which were newly isolated and identified as Vibrio harveyi, could have high proteinase activity.In the BGPY medium, the proteinase activity of the culture supernatant of one of these strains, FLN-108, was 15-fold higher than that of V. harveyi FLA-ll, and this strain produced two proteinases, which had different electrophoretic mobilities.In this paper, we describe the identification of the proteolytic, marine luminous bacterium, FLN-108, which was isolated as one of one 3009 hundred and forty-one luminous strains from surface coastal water at Okinawa, Japan, and the purification and someproperties of these two proteinases from this luminous strain. MATERIALS AND METHODSIsolation and identification of the organisms.

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A proteolytic, marine luminous bacterium was isolated from seawater and identified as Vibrio harveyi strain FLA-1 1. A proteinase from this strain, with a specific activity 61-fold higher than that of the culture supernatant, was purified to homogeneity. The purified enzyme had a molecular weight of 84,000, comprising a tetramer of 21,000 molecular weight subunits. The enzyme was most active at pH 8.0 and 55°C, and stable below 40°C. The enzyme activity was completely inhibited by EDTA, orthophenanthrolin and phosphoramidon. Metal ions such as Cu2+, Hg2+, Ni2+, Cd2+ and Co2+also inhibited the activity. These results indicate that this enzyme is a metal-chelatersensitive, alkaline proteinase.