From Cucurbita maxima

Biosynthesis of gibberellins Aip, A, Apl, Agg, and A07 hy a cell-free system from Cucurbita maxima." Phytochemistry, 1974, 13, ll+33-lUto. 

Fig. 5. Eight highly conserved regions of the primary structure of ACC synthase. Identical amino residue relative to the sequence of CM-ACSl (from Cucurbita maxima) is shown by dot. Eleven resuidues shown to be invariant among ACC synthase and aminotransferase are marked with X. The lysine residue (Box 6) which interacts with pyridoxalphosphate and with AdoMet is marked with. However, tyrosine residue in Box 5 are replaced by phenylalanine in AVO-ACSl (from avocado) and DC-ACSl (from carnation). The numbers between the adjacent boxes show number of residues present. AVO, avocado (Persea americana Mill) MELW, melon (Cucumis melo L.) GAC, geranium (Pelargonium x hortorum). For other abbreviation of source plants, see Table 1.

Baluano, G., O. Caputo, F. Viola, L. Delprino, and L. Cattel, Cyclization of squalene-2,3-epoxide to lOa-cucurbita-5,24-dien-3P-ol by microsomes from Cucurbita maxima seedlings. Phytochemistry, 22, 915-921 (1983). 

The enzymes catalyzing the steps after GAi2-aldehyde are 2-oxoglutarate-dependent dioxygenases, a type of enzymes known particularly well from the work with prolyl 4-hydroxylase in animal systems. In the case of GA biosynthesis, the participation of this class of enzymes was first shown for the entire pathways in cell-free systems from Cucurbita maxima [10] and Pisum sativum [12] and for 2 -hydroxylation in cell-free systems from peas and beans [11]. Their properties and distribution in different organisms were surveyed by MacMillan [15]. 

We have recently re-examined the effect of CCC and AMO-1618 on the incorporation of (R)-[2- C]mevalonic acid into /-kaurene in a cell-free system from Cucurbita maxima endosperm. The dose-inhibition curves for the two retardants (Fig. 3) confirm that AMO-1618 with an I50 of about 5 X 10 M (inhibitor concentration at which the reaction rate is reduced by 50%) is a much more effective inhibitor than CCC (I50 about 5x lO M). However, the concentration of CCC required to retard growth in wheat seedlings would be sufficient to inhibit ent-kaurene synthesis in the C. maxima system. Thus, the evidence suggests that for growth inhibition the primary site of action of CCC, except at very high concentrations, is the GA biosynthetic pathway. 

Hedden, P., and J.E. Grabbe Kaurenolide biosynthesis in a cell-free system from Cucurbita maxima seeds. Phytochem. 20, 1011 (1981). 

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