Endogenous enzyme activity

No antibodies, only application of developer. If positive, this shows endogenous enzyme activity. To solve this, raise levamisol concentration, with 20% acetic acid for 5 min, followed by intensive washing in water prior to the immunoprocedure (14). 

Blocking step 1 to block endogenous enzyme activity or endogenous biotin, use the corresponding blocking system (see Chap. 5) and wash in PBS or TBS for 2x3 min. 

Use of toxic chromogens is involved. Need to block endogenous enzyme activity. Extravagant when more than just a few target antigens are studied. 

Extremely laborious. Uses toxic chromogens. Need to block endogenous enzyme activity. 

Endogenous enzyme activity should interfere only minimally with... 

Block any endogenous enzyme activity as appropriate see Section 3.3.). Wash the section in water. 

Endogenous enzymic activity wifi probably not interfere in a solid phase enzyme immunoassay where the activity bound to the solid phase is measured. It is evident that endogenous enzymes can interfere in EMIT-type assays. 

Other minor enzyme systems can be used, such as P-galactosidase (5). This system works well. However, it can lead to some false-positive problems resulting from endogenous enzymes which have a similar reactivity (6). Another enzyme not commonly used is glucose oxidase. A glucose oxidase system can provide a sensitive and specific assay if other endogenous enzyme activity is a problem. 

Controls As with any technique it is essential to perform a number of controls. A positive control section should be included with each batch, to test for variations in the intensity of staining from day to day. For each test section, an appropriate immunohistochemical control should be performed to test for the presence of endogenous enzyme activities and/or nonspecific binding of the detection reagents. This is most easily achieved by the exclusion of the enzyme or the labeled nucleotide from the TUNEL/ISEL reaction mixture. 

Endogenous enzyme activity is suppressed as discussed in Section 17.3.4.3.2.1. 

Endogenous enzyme activity is readily recognizable in some cases (e.g. staining of peroxisomes with POase substrates) and can be inhibited specifically (Section 17.3.4.3.2.1). 

Staining of control slides without the application of the immune serum reveals endogenous enzyme activity cells devoid of the specific... 

Reduction of background staining due to nonspecific adsorption by pretreatment with normal serum by hypertonic buffers by addition of detergents (Triton X-100 Tween 20) to buffers by inhibition of endogenous enzyme activity (may be particularly prominent in cryostat sections). 

Ashie, I.N.A., Simpson, B.K., and Ramaswamy, H.S. Control of endogenous enzyme activity in fish muscle by inhibitors and hydrostatic pressure using RSM, /. Food Sci, 61, 350,1996. 

Direct immunoenzyme. Rapid. Permanent preparations. Simple nuclear counterstains may be used for studying tissue architecture in relation to immunolabeling. Use of toxic chromogens is involved. Need to block endogenous enzyme activity. Extravagant when more than just a few target antigens are studied. 

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