Rhizopus chinensis

The carboxyl proteases are so called because they have two catalytically essential aspartate residues. They were formerly called acid proteases because most of them are active at low pH. The best-known member of the family is pepsin, which has the distinction of being the first enzyme to be named (in 1825, by T. Schwann). Other members are chymosin (rennin) cathepsin D Rhizopus-pepsin (from Rhizopus chinensis) penicillinopepsin (from Penicillium janthinel-lum) the enzyme from Endothia parasitica and renin, which is involved in the regulation of blood pressure. These constitute a homologous family, and all have an Mr of about 35 000. The aspartyl proteases have been thrown into prominence by the discovery of a retroviral subfamily, including one from HIV that is the target of therapy for AIDS. These are homodimers of subunits of about 100 residues.156,157 All the aspartyl proteases contain the two essential aspartyl residues. Their reaction mechanism is the most obscure of all the proteases, and there are no simple chemical models for guidance. 

K. Suguna, E. A. Padlan, C. W. Smith, W. D. Carlson, and D. R. Davies, Binding of a reduced peptide inhibitor to the aspartic proteinase from Rhizopus Chinensis Implications for a mechanism of action, Proc. Natl. Acad. Sci. USA 84 7009 (1987). 

Catharanthus roseus) [9]. Maytansine (3) is an ansa macrolyde isolated from Maytenus ovatus [10], and rhizoxin (4) is an antitumor macrolide isolated from the fungus Rhizopus chinensis [11]. Another very important tubulin interactive anti-cancer agent is colchicine (6), and this compound binds to a different binding site of tubulin but is also used in anti-cancer therapy. 

Most of the EF-hand motifs have one water (—X). On the other hand, in Rhizopus chinensis aspartic proteinase (Suguna et al., 1987) there is one main-chain carbonyl oxygen bound to calcium and six water molecules to complete the pentagonal bipyramidal coordination. Calcium coordination has been measured in several viruses, such as Southern bean mosaic virus (Silva and Rossmann, 1985), satellite tobacco necrosis virus (Jones and Liljas, 1984), and tomato bushy stunt virus IV (Olson et al., 1983). 

A water molecule held between two carboxyl groups is possibly the nucleophile in the reaction catalyzed by the aspartic proteinase from Rhizopus chinensis (Suguna et al., 1987). 

Sato Z, Matsuda I, Noda T. Studies on macrocyclic lactone antibiotics. VII. Structure of a phytotoxin rhizoxin produced by Rhizopus chinensis. J. Antibiot. 1984 37 354-362. 

Noda T, Hashiba T, Sato Z. The structural changes in young 159. swollen roots of rice seedlings infected with Rhizopus chinensis... 

Rhizoxin D is a 16-membered macrolide isolated from the fungus Rhizopus chinensis Rh-2 and it showed remarkable antimitotic properties. Rhizoxin D was synthesized from four subunits and the final step involved the Stille coupling of the oxazole fragment with an iodolactone [17]. 

A microtubule inhibitor, rhizoxin (Fig. 1) was found in the culture filtrate of Rhizopus chinensis (j>). Subsequently, Iwasaki et al. (7 ) determined the chemical structure of this compound, and the antitubulin activity of rhizoxin was characterized using porcine brain tubulin (j3). 

Early experiments concerned the enzymatic hydrogenation of fumaric acid to succinic acid, catalyzed by either yeast 24,55 or enzyme extracts from yeast cells56. Much later, strains of Escherichia coli, Aerobacter aerogenes and Aerobacter cloacae were shown to have the same ability 57,58. An interesting mixed culture fermentation has been developed, where the fungus Rhizopus chinensis produces fumaric acid from glucose and a selected E. coli converts the previously formed fumaric acid into succinic acid58. 

Rhizopus chinensis and Escherichia coli (mixed culture fermentation)... 

Rhizoxin (107) is a 16-membered ring phytotoxin macrohde produced by Rhizopus chinensis [133]. It showed potent antifungal and antitumor activities by inhibiting tubufin polymerization [134]. 

Iwasaki, S., Kobayashi, H., Furukawa, J., Namikoshi, M., Okuda, S., Sato, Z., Matsuda, I., and Noda, T. (1984). Studies on macrocyclic lactone antibiotics. Vn. Structure of a phytotoxin rhizoxin produced by Rhizopus chinensis. J. Antibiot. 37, 354—362. 

S.a = Staphylococcus aureus. B.s = Bacillus subtilis, M.s Mycobacterium smegma its, S.m = Streptococcus mutant, P.g.= Porphyromonas gingivalis, A.a = Actinobacillus aclinornycetencomitans, M 1 = Micrococcus lysodeikticus, S 1 = Saccharomyces cerevesiae, Cu = Candida unit s. S.l = Sckrotmia hbertiarm, M.l = Mucor muceclo, R.c - Rhizopus chinensis = >100, -= >.50... 

USA, 84, 7009 (1987). Binding of a Reduced Peptide Inhibitor to the Aspartic Proteinase from Rhizopus Chinensis Implications for a Mechanism of Action. 

Rhizopus chinensis Fungi PDA, 5 days, 27°C >1,000 (1986) Thompson and Cannon... 

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