def statement_present_verb(stmt_type):
    """Return the present verb form of a statement type.

    Parameters
    ----------
    stmt_type : str
        The lower case string form of a statement type, for instance,
        'phosphorylation'.

    Returns
    -------
    str
        The present verb form of a statement type, for instance,
        'phosphorylates'.
    """
    override = {'complex': 'binds', 'regulateamount':
        'regulates the amount of', 'increaseamount':
        'increases the amount of', 'decreaseamount':
        'decreases the amount of', 'gef': 'acts as a GEF for', 'gap':
        'acts as a GAP for', 'inhibition': 'inhibits', 'gtpactivation':
        'activates when bound to GTP', 'regulateactivity':
        'regulates the activity of', 'activeform': 'has active form',
        'conversion': 'converts', 'influence': 'influences', 'modification':
        'modifies', 'addmodification': 'adds a modification to',
        'removemodification': 'removes a modification of',
        'selfmodification': 'modifies itself', 'event': 'happens'}
    return override.get(stmt_type) if stmt_type in override else stmt_type[:-3
        ] + 'es'
