Cloning and expression of the S-adenosylmethionine decarboxylase gene of Neurospora crassa and processing of its product |
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| Authors: | Hoyt M A Williams-Abbott L J Pitkin J W Davis R H |
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| Institution: | (1) Department of Molecular Biology and Biochemistry, University of California at Irvine, Irvine, CA 92697-3900, USA E-mail: rhdavis@uci.edu Tel.: +1-949-8245872; Fax: +1-949-8248551, US;(2) Monsanto Corporation, 700 N. Chesterfield Parkway, Chesterfield, MO 63198, USA, US |
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| Abstract: | S-adenosylmethionine decarboxylase (AdoMetDC) catalyzes the formation of decarboxylated AdoMetDC, a precursor of the polyamines
spermidine and spermine. The enzyme is derived from a proenzyme by autocatalytic cleavage. We report the cloning and regulation
of the gene for AdoMetDC in Neurospora crassa, spe-2, and the effect of putrescine on enzyme maturation and activity. The gene was cloned from a genomic library by complementation
of a spe-2 mutant. Like other AdoMetDCs, that of Neurospora is derived by cleavage of a proenzyme. The deduced sequence of the Neurospora proenzyme (503 codons) is over 100 codons longer than any other AdoMetDC sequence available in genomic databases. The additional
amino acids are found only in the AdoMetDC of another fungus, Aspergillus nidulans, a cDNA for which we also sequenced. Despite the conserved processing site and four acidic residues required for putrescine
stimulation of human proenzyme processing, putrescine has no effect on the rate (t
0.5∼10 min) of processing of the Neurospora gene product. However, putrescine is absolutely required for activity of the Neurospora enzyme (K
0.5∼100 μM). The abundance of spe-2 mRNA and enzyme activity is regulated 2- to 4-fold by spermidine.
Received: 4 August 1999 / Accepted: 14 February 2000 |
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| Keywords: | Neurospora Polyamines S-adeno-sylmethionine decarboxylase Proenzyme processing |
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