Although the patentee ultimately prevailed with a broader construction, the use of a definition section in the specification will almost certainly be taken as the requisite clear intent to redefine a given term, and any narrowing statements imported into the claims. If used at all, extra care and attention should be taken to draft definitions only to the extent absolutely necessary.
Background / Facts: The asserted patents are directed to a recombinant microbial host cell that uses a particular biosynthetic pathway to produce isobutanol, which is useful as a fuel or fuel additive. The claims recite catalysis by the polypeptide enzyme known as keto-acid reductoisomerase, or “KARI,” “having the [Enzyme Commission] EC number 1.1.1.86.” In general, KARI can utilize different electron sources for the catalysis, known as the “cofactor” or “coenzyme.” Two such cofactors are “NADH” and “NADPH.” The patent’s specification provides “definitions … to be used for the interpretation of the claims,” including a definition of KARI as a particular enzyme “using NADPH … as an electron donor.” The accused product uses mutant KARI enzymes that when using NADH as a cofactor exhibit significantly improved performance than when using NADPH alone as a cofactor.
Issue(s): Whether the specification’s definition of KARI as a particular enzyme “using NADPH … as an electron donor” limits the claimed KARI enzyme to be “NADPH-dependent” as opposed to using NADH or both NADPH and NADH.
Holding(s): No. “It cannot be disputed that the patentees offered a definition of KARI.” However, the court stated that it could “find no reason to constrict the phrase ‘using NADPH’ [as in the definition] to mean ‘only use NADPH’ or ‘NADPH-dependent.’” Instead, it found that the patents’ definition “excludes as-yet-undiscovered KARI enzymes that could catalyze … without using NADPH at all,” but “the description of specific types of KARI as NADPH-dependent does not clearly express an intent to redefine all KARI ‘using NADPH’ as KARI that must be NADPH-dependent.” “[T]he fact that an enzyme can catalyze … ‘using NADPH’ does not, on its own, indicate that the enzyme cannot also use other cofactors, such as NADH, to catalyze.”