HinCyc: A Knowledge Base of the Complete Genome and Metabolic Pathways of H. influenzae

Peter D. Karp, Christos Ouzounis, and Suzanne Paley

We present a methodology for predicting the metabolic pathways of an organism from its genomic sequence by reference to a knowledge base of known metabolic pathways. We applied these techniques to the genome of H. in uenzae by reference to the EcoCyc knowledge base to predict which of 81 metabolic pathways of E. coli are found in H. in uenzae. The resulting prediction is a complex hypothesis that is presented in computer form as HinCyc: an electronic encyclopedia of the genes and metabolic pathways of H. in uenzae. HinCyc connects the predicted genes, enzymes, enzyme-catalyzed reactions, and biochemical pathways in a WWW-accessible knowledge base to allow scientists to explore this complex hypothesis.

The description and results of an implementation of such a gene-finding model, called Genie, is presented. The exon sensor is a codon frequency model conditioned on windowed nucleotide frequency and the preceding codon. Two neural networks are used, as in, for splice site prediction. We show that this simple model performs quite well. For a cross-validated standard test set of 304 genes in human DNA, our gene-finding system identified up to 85% of protein-coding bases correctly with a specificity of 80%. 58% of exons were exactly identified with a specificity of 51%. Genie is shown to perform favorably compared with several other gene-finding systems.

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