Gregorios 150 was the son of Photeinos 22; during the questioning of Maximos 10 (Maximus the Confessor) at Constantinople in 652/653 Gregorios 150 claimed that he had once visited Maximos 10 in his cell at Rome; in conversation Gregorios 150 had remarked that the emperor was a priest, to which Maximos 10's disciple Anastasios 1 had replied that the emperor was unworthy.

Maximos 10 denied the truth of this statement and gave his own account, saying that Gregorios 150 had come to Rome and paid him a visit, during which he had asked Gregorios 150 the reason for his visit to Rome; Gregorios 150 had replied that he had been sent by the emperor to persuade the bishop of Rome to be united with the patriarch of Constantinople on the basis of the Typos, to which Maximos 10 had answered that this was impossible as the Typos was heretical; Gregorios 150 had insisted that he adhered firmly to the Creed (τὸ σύμβολον), but Maximos 10 had demonstrated that the Typos was not consistent with the Creed, and moreover that emperors were not priests: Relatio Motionis IV, 113D.

In 652/653, at the date of the interrogation of Maximos 10, Gregorios 150 was an asekretis: Relatio Motionis X, 124 (Maximos 10 refers to his reply πρὸς τὸν κῦριν Γρηγόριον τὸν ἀσηκρῆτιν).

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