A method is described controlling enzymatic decomposition of peroxide comprising contacting a composition containing a peroxide decomposing enzyme with an aldehyde functional polymer added in an amount effective to control the enzyme. There also is a method described for bleaching cellulose pulp, such as recycled paper pulp or other pulps, with an aldehyde functional polymer introduced in an amount effective to control peroxide decomposing enzymes present in the pulp being bleached. Paper products containing the aldehyde functional polymer used to control peroxide decomposing enzymes in a bleaching treatment of cellulose pulp are also provided.