Classification of proteolytic enzyme function
Non-limiting hydrolyzing protease:
It means that the specificity of the enzyme is very poor, and it can hydrolyze many polypeptide bonds in the protein to produce various small peptides and even free amino acids. The physiological function of this kind of protease is mainly involved in the degradation of proteins in the body. For example, various proteases secreted by the gastrointestinal system digest and decompose the food protein ingested in vitro; various cathepsins in the cell lysosome can eliminate various metabolisms in the body. product. Red blood cells with an average lifespan of 120 days are degraded by cathepsin.
It refers to the specificity of the enzyme, which only acts on a specific protein substrate, hydrolyzes the specific peptide bond, and then produces various active polypeptides or proteins with different physiological functions. Such proteases play a biological regulation in vivo, and most of them belong to serine proteases, and their specificity is similar to that of trypsin, that is, a peptide bond composed only at the carboxyl terminus of arginine or lysine.
Biological effects are transient: rapid activity is demonstrated by activation of active protein precursors in the body.
It is expressed in a cascade reaction: which means the protein that is activated in the first-stage reaction is itself a protease that catalyzes the next-stage reaction, thus acting as a step-by-step amplification.
There are positive and negative feedback systems: proteases involved in biological regulation can sometimes produce the same physiological effects through two different pathways, which complement each other.
Proteolytic enzyme method:
(1) One-step enzyme method: 1% enzyme solution was directly added to the mixture of serum and washed red blood cells, incubated in a 37 ° C water bath for 30 min, centrifuged at 3000 r / min for 15 s to observe the agglutination reaction.
(2) Enzyme two-step method: Add 1 part of 1% enzyme solution to 1 part of washed packed red blood cells, and incubate in a 37 ° C water bath for 10 min. The enzyme-treated red blood cells were washed 3 times with physiological saline to prepare 2% to 5% red blood cell suspension, 2 drops were taken, 1 drop of serum was added and incubated at 37 ° C for 15 min, centrifuged at 3000 r / min for 15 s to observe the agglutination reaction.