Usually TCA is trichloroacetic acid, if this is the case TCA cause protein denaturation and precipitation, which can be good for glycogen estimation but absolutely not for enzyme activity measurements

Denaturation of proteins by TCA is a well established phenomenon in Chemistry.

 J Biochem (1971) 70 (1): 63-73.

 It will be better if you estimate  glycogen   by the use  of Anthrone Reagent  by Seifter method as: 

Reagents: KOH 30% ;Anthrone Reagent ;Conc. Sulphuric Acid ;Ethyl Alcohol  and

Standard glucose (40mg/ml)

Procedure:  The tissues are digested in boiling KOH. Glycogen is precipitated in alcohol; dissolved in water and heated with anthrone reagent, so as to convert glycogen into glucose. The latter gives colour reaction.

 Take three test tubes labelled as ‘T’, ‘S’,’B’ for test, standard and blank  

respectively. Take 1ml of aliquot in the test, 1ml of standard glucose solution

in standard and1 ml distilled water in blank. All test tubes were transferred to

an ice bath, 4ml of anthrone reagent was carefully added and shaken

thoroughly and heated in boiling water bath for exactly 4 minutes. Once again

the tubes were placed in ice bath and cooled. The intensity of the green colour

developed and read at 620nm. The amount of glycogen present in tissues wereexpressed as mg glycogen/100mg fresh tissue weight.