Konstantinos 24 was priest and ekdikos (defensor) of the Church of Hagia Sophia, he was a Latin grammatikos: Riedinger, p. 290, lines 25-27, p. 336, lines 16-18 (= Mansi XI 396, 421) (ἑρμηνεύοντος Κωνσταντίνου τοῦ θεοσεβεστάτου πρεσβυτέρου καὶ ἐκδίκου τῆς ἐνταῦθα ἁγιωτάτης μεγάλης ἐκκλησίας καὶ γραμματικοῦ Ῥωμαϊκοῦ or similar). The old Latin version printed in Riedinger, p. 291, lines 22-24, p. 337, lines 16-18 (= Mansi XI 395, 422) reads: "interpretante Constantino deo amabile presbitero et defensore sanctissimae huius magnae ecclesiae et Latino grammatico" (or similar).

At the tenth session of the Third Council of Constantinople (the Sixth Ecumenical Council), on 18 March 681, he translated for the Council when texts of Latin Fathers, produced by the representatives from Rome, were compared with Latin versions of the texts apparently kept in the patriarchal library at Constantinople: Riedinger, p. 290 (= Mansi XI 396) (St Ambrose), Riedinger, p. 336 (= Mansi XI 422) (St Augustine). Styled a priest and Latin grammatikos (πρεσβύτερος τῆς ἐνταῦθα ἁγιωτάτης μεγάλης ἐκκλησίας καὶ γραμματικὸς Ῥωμαϊκός), he told the fourteenth session of the Council (on 5 April 681) how, at the request of the patriarch Paul II (Paulos 2; 641-653), he examined a Latin codex of the Fifth Ecumenical Council found in the patriarchal library and discovered that the libelli of Vigilius were not included in the acts of the seventh session; on orders from Paulos 2 he translated them into Latin (μετέφρασα Ῥωμαϊστὶ: Riedinger, p. 652, line 19) and had them copied by Sergios 12 and bound in by the calligrapher Theodoros 53; his account was verified by Sergios 12, who quoted Paulos 2 as calling Konstantinos 24 ὁ κῦρις Κωνσταντῖνος ὁ γραμματικὸς ὁ Ῥωμαϊκὸς (implying that at the time Konstantinos was a grammaticus Latinus and had not yet taken Holy Orders): Riedinger p. 654, lines 6-7. The whole episode is recounted in Riedinger, pp. 650-654 (= Mansi XI 593-596).

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