01Identify the enzymatic challenge

O’Donoghue and colleagues developed a peptide-library method that uses liquid chromatography–tandem mass spectrometry to characterise peptidase specificity. The original study illustrates that cleavage information depends on the relationship between the enzyme and its tested substrates.O’Donoghue and colleagues — Global identification of peptidase specificity by multiplex substrate profiling (opens in a new tab)

A purified protease, a defined enzyme mixture and a tissue homogenate represent different challenges. Keep those descriptions separate when collecting results from several papers.

For a named enzyme, record the actual preparation and relevant experimental context. For a biological mixture, retain the source and preparation description rather than assigning every effect to one protease by assumption.

The peptide identity also needs precision. Terminal modifications, labels or sequence differences should remain part of the tested entity when you compare results.

A paper examining one construct can provide evidence about that construct. It does not automatically establish how a differently modified material with the same short name will behave.

02Distinguish disappearance from cleavage evidence

The table is a reading framework, not a requirement that every study use the same instrument. Its purpose is to separate a detector observation from a molecular assignment.

If only the parent signal is measured, examine what the study did to distinguish enzymatic cleavage from other reasons for lower recovery. Missing signal alone does not identify the location of a broken bond.

If fragments are reported, check how their identities were established. A predicted mass can guide a hypothesis, but the paper should make clear which assignments were directly supported.

Also retain whether fragment abundance was quantified or merely detected. The presence of a product and its contribution to the material balance are different questions.

03Keep the time course and model conditions together

Errante and colleagues’ dermal-stability study used LC-MS/MS and examined factors including peptide concentration and properties of skin-homogenate preparations. Its abstract explicitly describes evaluating these factors before comparing degradation profiles.Errante and colleagues — Susceptibility of cosmeceutical peptides to proteases activity (opens in a new tab)

Read the sampling times and the portion of the curve that was actually observed. A stable-looking endpoint may mean little if the window misses an earlier change or cannot resolve a small remaining amount.

For a fitted half-life, identify the measured quantity and the model used. A parameter obtained from parent disappearance should retain that definition rather than become an unrestricted biological lifetime.

A comparison between peptides is easiest to interpret when the relevant conditions are aligned. If different preparations were used, keep that difference visible instead of ranking the molecules solely by the reported time values.

04Separate chemical persistence from biological function

The amount of intact parent is a chemical observation. Whether that parent remains biologically active is a separate question unless the experiment measures the relevant function.

Likewise, cleavage does not by itself establish the behaviour of every product. If a paper proposes that a fragment contributes to a response, look for evidence about the fragment rather than infer its activity from its existence.

A tissue homogenate also does not reproduce every feature of an intact organism. A susceptibility result can help explain a molecular vulnerability without establishing exposure at a target or a clinical effect.

The clearest summary identifies the parent peptide, challenge system, time window and evidence for transformation. It reports persistence or cleavage under those conditions and leaves broader claims to the additional experiments needed to support them.