In vitro metabolism of inositol 1,4,5-trisphosphate by Neurospora crassa

• Published in: FEMS microbiology letters Vol. 154; no. 2; pp. 223 - 229
• Main Authors: Hosking, Sarah L, Trinci, Anthony P.J, Robson, Geoffrey D
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-09-1997
• Subjects: Inositol trisphosphate; Neurospora; Ins(1,4,5)P 3, inositol 1,4,5-trisphosphate; Inositol trisphosphate; PtdInsP 2, phosphatidylinositol bisphosphate; InsP, inositol 4-phosphate; Neurospora; Ins(1,4)P 2, inositol 1,4-bisphosphate; PtdInsP, phosphatidylinositol phosphate; PtdIns, phosphatidylinositol; InsP, inositol 1-phosphate; Ins(4,5)P 2, inositol 4,5-bisphosphate; Ins(1,4,5,X)P 4, inositol tetrakisphosphate, isomer unknown; Ins(1,5)P 2, inositol 1,5-bisphosphate; Ins(1,3,4,5)P 4, inositol 1,3,4,5-tetrakisphosphate
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1016/S0378-1097(97)00329-7

The in vitro metabolism of Ins(1,4,5)P
3 by a soluble and a particulate fraction of
Neurospora crassa revealed the presence of an Ins(1,4,5)P
3 kinase activity which was associated with the soluble fraction of this organism but was not detected in the particulate fraction. The product was tentatively identified as Ins(1,3,4,5)P
4 by co-chromatography with an authentic standard. A second minor unidentified InsP
4 was also detected. The kinase was not stimulated by Ca
2+/calmodulin and was unaffected by EGTA. Phosphomonoesterase activity was predominantly associated with the particulate fraction producing Ins(1,4)P
2, Ins(1,5)P
2 and Ins(4,5)P
2 indicating the presence of 1′, 4′ and 5′- phosphomonoesterases.
N. crassa therefore differs from other classes of eukaryotes where Ins(1,4,5)P
3 metabolism has been studied in possessing a specific 4′-phosphomonoesterase. In the particulate fraction, 1′-phosphomonoesterase was the principal route for Ins(1,4,5)P
3 degradation whereas all three phosphomonoesterases were equally active in the soluble fraction. All phosphomonoesterase activity was Mg
2+-dependent. Further degradation to inositol monophosphates was not observed under the conditions used in this study.