There are no indications in the phonology of Palenquero sabé 'to know' that the item was derived from Portuguese rather than Spanish.
Note that saber is bifunctional in Palenquero. That is, it has the lexical meaning of 'to know', and also a strictly aspectual function, i.e. HABITUAL, comparable to Spanish soler.
Preverbal asé or sabé (the latter being a far less frequent though not uncommon marker) are used to express habitual aspect. Habitual aspect is, however, often simply implied, i.e. not expressed overtly by asé or sabé.
Note: the HABITUAL use of Palenquero sabé is a feature that was once common in Spanish. See:
Lida Malkiel (1948/1949: 269–283).
Source: Schwegler & Green 2007: 280