188 Agritrop, Vol. 26, No. 4 (2007) Agritrop, 26 (4) : 187 -193 (2007) issN : 0215 8620 Fakultas Pertanian Universitas Udayana Denpasar Bali - Indonesia C Peranan Sucrose Phosphate Synthase (SPS) dan Acid Invertase (AI) Internoda Tebu (Saccharum offcinarum L.) dalam Akumulasi Sukrosa MISWAR 1 , BAMBANG SUGIHARTO 2 , TRI HANDOYO 1 , DAN SRI AYU MADE 3 1 Fakultas Pertanian Universitas Jember 2 Fakultas Matematika dan Ilmu Pengatahuan Alam Universitas Jember 3 Alumni Fakultas Pertanian Universitas Jember ABSTRACT Roles of Sucrose Phosphate Synthase (SPS) and Acid Invertase (AI) of Sugarcane (Saccharum offcinarum L.) Internodes in Sucrose Accumulation Sucrose content is an important component of yield in sugarcane (Saccharum offcinarum L.) juice and its synthesis is determines by the activity of Sucrose phosphate synthase (SPS; EC. 2.4.1.14). This enzyme catalyzes the penultimate reaction of the formation of sucrose from fructose-6-phosphate (F6P) and uridine-5-diphospho glucose (UDPG). Sucrose is synthesized on leaf and translocated into stalk at where it is accumulated to be accumulated it. In contrast to SPS, acid invertase (AI) is an enzyme that hydrolyze sucrose to glucose and fructose. The ability of sugarcane to accumulate the sucrose in stalk is determined by the differences between SPS and AI activities. This study was aimed know role of the internodes SPS and AI in sucrose accumulation in the internodes of some sugarcane varieties. SPS, AI and sucrose were extracted from internodes 1, 3 and 5 of 9 month old sugarcane. The results showed that sucrose content for all varieties increased concomitant with the rise in the age of internodes. The decrease in AI activity in internode caused the increase in sucrose content in internodes. Meanwhile, higher sucrose content in the older internodes was not followed by higher in SPS activity. Generally, there was strong negative correlation between sucrose content of internodes with SPS and AI activity. In conclusion, the ability of sugarcane to accumulate sucrose at internodes was primary determined by AI activity, while SPS activity had a small role on sucrose accumulation at internodes. Keywords: sugarcane, sucrose phosphate synthase, acid invertase, sucrose, internodes PENDAHULUAN Sukrosa merupakan produksi akhir asimilasi karbon (C) pada proses fotosintesis yang terjadi di daun (Kim et al., 2000) dan bentuk karbohidrat yang mudah ditransporta-sikan ke jaringan simpan atau sink tissues (Cheng et al., 1996). Selain berfungsi dalam penyediaan energi dan kerangka karbon, sukrosa juga berperan dalam pengaturan ekspresi gen lainnya (Koch, 1996; Ohto et al., 2001), partisi karbon asimilate (Lunn and Hatch, 1997; Grof et al., 1998) serta pertumbuhan dan perkembangan tanaman (Fung et al., 2003). Dalam tanaman sucrose phosphate synthase (SPS; EC 2.3.1.1) merupakan enzim utama yang menentukan biosintesis sukrosa yang berlangsung di mesofil daun. Enzim ini mengkatalisis pembentukan sucrose-6-phosphate (suc6P) dari fructose-6-phosphate (F6P) dan uridine- 5-diphospho glucose (UDPG). Selanjutnya phosphate pada suc6P diputus oleh sucrose phosphate phosphatase (SPP) sehingga dihasilkan sukrosa (Langenkamper et al., 2002; Chen et al., 2005). Besar kecilnya aktivitas SPS menentukan kandungan sukrosa daun (Grof et al., 1998) dan berkorelasi positif dengan rasio sukrosa:pati daun (Galtier et al., 1995). Akumulasikan sukrosa pada batang tebu dimulai pada internoda yang sedang mengalami proses pemanjangan (elongation) sampai pada internoda yang proses pemanjangannya berhenti (Lingle, 1997; Rose & Botha, 2000). Besarnya jumlah sukrosa yang dapat diakumulasikan pada batang sangat ditentukan oleh selisih antara proses sintesis dan degradasi sukrosa